Starter of stuffed sweet potato (4)
I believe the answer is:
spud
'potato' is the definition.
(I know that potato can be written as spud)
'starter of stuffed sweet' is the wordplay.
'starter of' says to take the initial letters.
'sweet' becomes 'pud' (pud is a kind of sweet).
The first letter of 'stuffed' is 's'.
's'+'pud'='SPUD'
(Other definitions for spud that I've seen before include "Potato (informal)" , "Starchy bit of food" , "Tattie" , "Weed spade" , "The common potato" .)