...put on for exercise? (5)
I believe the answer is:
apply
I believe this clue is a double definition.
'put on' is the first definition.
(synonyms)
'for exercise?' is the second definition.
(exercising is a kind of applying)
(Other definitions for apply that I've seen before include "Send off (form, etc)" , "describing the cooker?" , "Use - ask (for)" , "Put (eg, paint) on" , "Put to use" .)