One of a group (6)
I believe the answer is:
member
'one of a group' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for member that I've seen before include "Person in an organised group" , "A body part or kind of participant" , "Eg, leg, arm" , "Elected person" , "either left or right wing, say" .)