Cream is a non-starter for dieters (4)
I believe the answer is:
lite
'for dieters' is the definition.
(I've seen this in another clue)
'cream is a non-starter' is the wordplay.
'cream' becomes 'elite' (as in the cream of the crop).
'is a non-starter' means to remove the first letter (the letter which starts the word is ignored).
'elite' with its initial letter removed is 'LITE'.
(Other definitions for lite that I've seen before include "With fewer calories" , "Low in calories" , "Low in strength" .)