Puff, brilliant idea (6)
I believe the answer is:
wheeze
This clue might be a double definition.
'puff' is the first definition.
(thesaurus)
'brilliant idea' is the second definition.
'wheeze' can be an answer for 'idea' (I have seen 'good idea' mean 'wheeze' so perhaps 'idea' could also mean 'wheeze'). I am not sure about the 'brilliant' bit.
Can you help me to learn more?
(Other definitions for wheeze that I've seen before include "Struggle for breath - cunning plan" , "Breathe with hoarse whistling sound" , "A crafty trick!" , "Breathe with hoarse sound, or a clever idea" , "Cunning scheme (informal)" .)