Fed-up man truly cutting game in a truculent manner (9)
I believe the answer is:
defiantly
'fed-up man truly cutting game' is the definition.
I can't judge whether this defines the answer.
'truculent manner' is the wordplay.
'truculent' becomes 'defiant' (similar in meaning).
'manner' becomes 'ly' (I can't justify this - if you can you should believe this answer much more).
'defiant'+'ly'='DEFIANTLY'
'in a' acts as a link.
Can you help me to learn more?
(Another definition for defiantly that I've seen is " In rebellious way".)