Wimp exploits work (7)
I believe the answer is:
milksop
'wimp' is the definition.
(I've seen this before)
'exploits work' is the wordplay.
'exploits' becomes 'milks' (milking is a kind of exploiting).
'work' becomes 'op' (abbreviation for opus).
'milks'+'op'='MILKSOP'
(Other definitions for milksop that I've seen before include "Weed" , "Wimpish fellow" , "Feeble youth" , "Cissy, fond of a pinta?" , "soft fellow" .)