Chip in a chip (4)
I believe the answer is:
ante
'chip in a chip' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ante that I've seen before include "not post" , "Preceding birth" , "Player's stake in poker - a ten? (anag)" , "Stake, bet" , "A neat sort of prefix" .)