There was little to choose between Chichester and their opposition from East Sussex in the opening phases.
United, a couple of places below Chi in the SCFL Premier, were forced into significant changes with their line-up.
Chichester manager Miles Rutherford also had to make some adjustments and it was Alex Collard, playing up front rather than in his customary centre-back role, who had game’s first chance.
Clack had an effort saved by Phil Hawkins moments later and at the other end Jack Lee did well to clear the danger after an Eastbourne corner before the visitors went close from a free-kick.
Get all the local football in the Observer - out on Thursday - including reports on the Rocks, Chi City, Pagham, Selsey, Midhurst, Bosham, Nyetimber Pirates, Chi Ladies - and a report on a new walking football initiative in Chichester. Plus fixtures, results and tables
United didn’t really look like a side with only one win in six and a lovely back-heel in a neat exchange between Max Hollobone and Steve Dallaway set up a shot for the away side that flashed over the bar.
Then less than 60 seconds later the ball was in the back of the Eastbourne net. Kieran Hartley cut in from the left flank and Ben Pashley found Clack who drilled a pile-driver under Hawkins for his third goal in as many games.
The last 30 minutes of the first half were scrappy to say the least with few clear cut chances and neither team was able to produce much free-flowing football.
After the interval Lee had City’s first effort but pulled his shot wide when the ball broke to him just inside the box following a Chi corner in the 50th minute. Then Danny Andrews and Dean Stevens carved out opportunities for United in quick succession around the hour mark.
Clack’s second goal in the 69th minute came in controversial circumstances that generated a bemused reaction from home fans and an incensed one from Eastbourne players, supporters and management.
For whatever reason neither referee Josh Godfrey nor his assistant considered the City winger to be offside and the goal stood despite all the protests.
There was a chance for a Clack hat-trick ten minutes after this gift when he ran on to a well-measured through ball only to drag his shot the wrong side of the post. Chris Hooker spurned an opportunity just beforehand and in the closing stages Omar Barry had a goal-bound attempt blocked by a teammate.
Clack was the match’s stand-out player. He’d scored twice against Eastbourne in the reverse fixture back in November at The Oval and has now netted 16 goals for Chi in the league this season.
City coach Danny Potter was happy to pick up another three points and delighted with a third clean sheet in a row. “The side did well again and we’ve got some momentum heading into the sharp end of the season,” said Potter.
Eastbourne United manager Tobi Hutchinson said: ‘We were missing a number of first team starters and we were a bit naive and gave that opening goal away through lack of concentration. But I was proud of the boys that stepped up from the under-21s.”
Oaklands Park has become something of a fortress this season and Chi have lost only one home league game. City are on the same points as second-placed Haywards Heath with six games to go.
Next up for City is an away match against Peacehaven and Telscombe.
Chichester City – Ender, Williams (Northeast), Lee, French, Martin, Pashley (Barry), Hartley, Horncastle, Hooker, Clack, Collard (Buffin).