Silly consuming son’s bananas (6)
I believe the answer is:
insane
'bananas' is the definition.
(I've seen this in another clue)
'silly consuming son's' is the wordplay.
'silly' becomes 'inane' (inane means silly or foolish).
'consuming' means one lot of letters goes inside another.
'inane' placed around 's' is 'INSANE'.
(Other definitions for insane that I've seen before include "Mentally ill" , "Sienna (anag.)" , "without any reason" , "mad for love?" , "Round the bend" .)