Shrivel, become limp (4)
I believe the answer is:
wilt
I believe this clue is a double definition.
'shrivel' is the first definition.
(I've seen this in another clue)
'become limp' is the second definition.
(synonyms)
(Other definitions for wilt that I've seen before include "Lose strength and become limp" , "Decline" , "Droop in the heat" , "Ave --; black --" , "Flag" .)