Helped fool with nutty diets (8)
I believe the answer is:
assisted
'helped' is the definition.
('assist' can be a synonym of 'help')
'fool with nutty diets' is the wordplay.
'fool' becomes 'ass' (ass is a kind of fool**).
'with' means one lot of letters go next to another.
'nutty' is an anagram indicator.
'diets' with letters rearranged gives 'isted'.
'ass'+'isted'='ASSISTED'
(Other definitions for assisted that I've seen before include "Aided" , "given help" , "Lent a hand" , "Helped" , "to small sibling involved in stormy dates" .)