Upset a small pie (8)
I believe the answer is:
This clue is a double definition.
'upset' is the first definition.
(upset can mean to turn something over)
'a small pie' is the second definition.
(eg apple turnover)
(Other definitions for turnover that I've seen before include "(Annual) money taken by business; small pie" , "apple-pie" , "sales of > pastry?" , "receipts" , "sweet" .)