Take off jumper, did you say? (4)
I believe the answer is:
flee
'take off' is the definition.
(I've seen this in another clue)
'jumper did you say?' is the wordplay.
'jumper' becomes 'flea' (something that jumps).
'did you say?' shows a homophone (sound like).
'flea' is a homophone of 'FLEE'.
(Other definitions for flee that I've seen before include "retreat" , "Run quickly away" , "Turn tail" , "Maybe escape" , "Run (from danger)" .)