Doctor eats large English sweet (5)
I believe the answer is:
dolce
'sweet' is the definition.
(I've seen this before)
'doctor eats large english' is the wordplay.
'doctor' becomes 'doc' (synonyms).
'eats' is an insertion indicator.
'large' becomes 'l'.
'english' becomes 'E' (abbreviation).
'doc' placed around 'l' is 'dolc'.
'dolc'+'e'='DOLCE'
(Other definitions for dolce that I've seen before include "sweetly and softly" , "Stop" , "To be played sweetly" , "La ... Vita (Fellini film)" , "Musical instruction to play gently and sweetly" .)