Shrivel up (7)
(Other definitions for crumple that I've seen before include "Collapse, cave in" , "wrinkle" , "Fold, collapse" , "Become crushed" , "Go to pieces" .)
'shrivel up' is the definition.
(I know that shrivel up can be written as wither)
This is the entire clue.
(Other definitions for wither that I've seen before include "Shrivel and decay" , "Writhe about and shrivel" , "Waste" , "(Of a plant) shrivel up" , "Droop, shrivel" .)