They resist difficult puzzles after work (8)
I believe the answer is:
opposers
'they resist' is the definition.
(people who oppose or resist things)
'difficult puzzles after work' is the wordplay.
'difficult puzzles' becomes 'posers' (poser can mean a difficult puzzle or problem).
'after' says to put letters next to each other.
'work' becomes 'op' (short for opus).
'posers' after 'op' is 'OPPOSERS'.
(Other definitions for opposers that I've seen before include "dissenters" , "adversaries" .)