Is a lemon terribly sweet? (8)
I believe the answer is:
semolina
'sweet?' is the definition.
(I've seen this before)
'is a lemon terribly' is the wordplay.
'terribly' is an anagram indicator.
'is'+'a'+'lemon'='isalemon'
'isalemon' with letters rearranged gives 'SEMOLINA'.
(Other definitions for semolina that I've seen before include "Wheat food found in a soil, men" , "Wheat product used in pasta" , "Part of wheat used in puddings" , "Is no meal (anag.)" , "What could be for pudding" .)