In exam, use menthol for fun (9)
I believe the answer is:
amusement
'fun' is the definition.
(thesaurus)
'in exam use menthol' is the wordplay.
'in' indicates a hidden word.
'AMUSEMENT' is hidden within 'exam use menthol'.
'for' is the link.
(Other definitions for amusement that I've seen before include "(State of) finding something funny" , "Light-hearted pastime" , "set up through arcade?" , "Diversion, recreation" , "Pleasure, diversion" .)