Ask to box good fighter, turning up to prevent cheating (10)
I believe the answer is:
invigilate
'prevent cheating' is the definition.
I can't tell whether this definition defines the answer.
'ask to box good fighter turning up' is the wordplay.
'ask' becomes 'invite' (inviting is a kind of asking).
'to box' indicates putting letters inside ('box' can mean contain, as in to put in a box).
'good' becomes 'g' (abbreviation).
'fighter' becomes 'Ali' (boxer Muhammad Ali).
'turning up' shows that the letters should be reversed in order.
'ali' in reverse letter order is 'ila'.
'g'+'ila'='gila'
'invite' enclosing 'gila' is 'INVIGILATE'.
'to' acts as a link.
Can you help me to learn more?
(Another definition for invigilate that I've seen is " Supervise an exam".)