Opportunity expired to have small pie (8)
I believe the answer is:
turnover
'small pie' is the definition.
(eg apple turnover)
'opportunity expired' is the wordplay.
'opportunity' becomes 'turn' (having a turn means having an opportunity).
'expired' becomes 'over' (over can mean finished or expired).
'turn'+'over'='TURNOVER'
'to have' acts as a link.
(Other definitions for turnover that I've seen before include "Business - reversal" , "Profit" , "Folded pie" , "sales of > pastry?" , "Takings" .)