Jofra Archer's eventful half century - he was bowled twice off a no ball - piloted Sussex from their overnight 342-7 to 430 all out.
Then Worcestershire were reduced to 231-8, 50 short of avoiding the follow on, with Harry Finch taking five catches in an innings - the sixth time a Sussex outfield player has achieved that feat.
Only Clarke looked entirely comfortable against the Sussex pace duo of Chris Jordan and Archer in racing to 77 off 79 balls with 12 fours.
It followed on from successive scores of 142, 110 not out, 45, 23 and 93 not out in his five previous Championship innings.
Clarke eventually became one of three victims for Jordan (17-5-61-3) while Archer finished with 2-54
The home side initially ran into trouble after openers Daryl Mitchell and Brett D'Oliveira had put on 39.
Mitchell (7) drove at Archer and nicked through to Finch at second slip and D'Oliveira (27) departed in the same fashion off David Wiese.
Tom Fell (12) then fell victim to a superb reflex catch by Archer at mid wicket as he worked Jordan off his legs.
Clarke instantly looked in prime form and galloped to his fifty with nine boundaries including three in one over from Stuart Whittingham.
The England Lions batsman was given staunch support by George Rhodes in a stand of 77 in 17 overs before the latter on 13 chopped spinner Danny Briggs onto his stumps.
Ben Cox (0) nicked an Archer delivery to present a third catch to Finch who then produced a brilliant diving effort in the same position to end Clarke's fine knock off the bowling of Jordan.
Skipper Joe Leach (1) was lbw to Jordan before Ed Barnard and John Hastings, who was accompanied by a runner, added 48.
After a brief stoppage, the players returned and Hastings (34) was instantly dismissed as Finch claimed his fifth catch at backward point off Stiaan van Zyl.
Earlier Archer survived being bowled twice off a no ball by Barnard on seven and 29 but in between he played some powerful strokes.
Jordan added only a single to his overnight 57 before he was bowled by Josh Tongue and Fell produced a superb catch at mid wicket to dismiss Danny Briggs (16) off Leach.
Pat Brown claimed his first Championship wicket to wrap up the innings with Archer finally holing out to Fell at deep square leg for 59.