Exercise fan consuming a snack (6)
I believe the answer is:
peanut
'snack' is the definition.
(I've seen this before)
'exercise fan consuming a' is the wordplay.
'exercise' becomes 'pe' (Physical Education).
'fan' becomes 'nut' (I've seen this before).
'consuming' indicates putting letters inside.
'pe'+'nut'='penut'
'penut' placed around 'a' is 'PEANUT'.
(Other definitions for peanut that I've seen before include "sort of butter" , "Groundnut" , "little bit of food" , "One of little importance -- ante up (anag)" , "Ante up for the popular kernel" .)