Cream? End of regime low in calories (5)
I believe the answer is:
elite
'cream?' is the definition.
(cream is a kind of elite)
'end of regime low in calories' is the wordplay.
'end of' says to take the final letters.
'low in calories' becomes 'lite' (I've seen this before).
The final letter of 'regime' is 'e'.
'e'+'lite'='ELITE'
(Other definitions for elite that I've seen before include "Cream, the pick" , "Group enjoying superior status" , "Selected as the best" , "A privileged or select group" , "one of the letter sizes" .)