They are not in favour of work with difficult puzzles (8)
I believe the answer is:
opposers
'they are not in favour' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'work with difficult puzzles' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'with' is a charade indicator (letters next to each other).
'difficult puzzles' becomes 'posers' (poser can mean a difficult puzzle or problem).
'op'+'posers'='OPPOSERS'
'of' is the link.
Can you help me to learn more?
(Other definitions for opposers that I've seen before include "adversaries" , "dissenters" .)