One resisting work has a problem (7)
I believe the answer is:
opposer
'one resisting' is the definition.
(I've seen this before)
'work has a problem' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'has' is a charade indicator (letters next to each other).
'a problem' becomes 'poser' (poser is a kind of problem).
'op'+'poser'='OPPOSER'
(Other definitions for opposer that I've seen before include "One resisting" , "One offering resistance" , "Adversary" , "Propose to challenger" , "Second to speak" .)