Sit for an artist (4)
I believe the answer is:
pose
'sit for an artist' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pose that I've seen before include "Sit (for an artist)" , "front" , "Affectation" , "Attitudinise" , "Models do it for photographic or artistic purposes" .)