Every other piece of jelly in the cream (5)
I believe the answer is:
'cream' is the definition.
(as in the cream of the crop)
'every other piece of jelly in the' is the wordplay.
'every other piece of' means one should take alternating letters (every second letter is used).
The alternating letters of 'jellyinthe' are 'ELITE'.
(Other definitions for elite that I've seen before include "Aristocracy" , "Identified as the best" , "A privileged group in society" , "A privileged class of people" , "High society" .)