Favourite silly food (7)
I believe the answer is:
peanuts
'favourite silly' is the definition.
Although both the answer and 'silly' are nouns, they are not in the same form of the noun.
'food' is the wordplay.
I cannot really understand how this works, but
'food' could be 'pea' (pea is a kind of food) and 'pea' is present in the answer.
The remaining letters 'nuts' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for peanuts that I've seen before include "Very small amount of money" , "pittance" , "Snack food - comic strip with Snoopy and Charlie Brown" , "Paltry sum of money" , "Cartoon - giving a kind of butter" .)