A couple upset after end of big cheese (5)
I believe the answer is:
gouda
'cheese' is the definition.
(Gouda is an example)
'a couple upset after end of big' is the wordplay.
'couple' becomes 'duo' (two people).
'upset' is a reversal indicator.
'after' means one lot of letters go next to another.
'end of' suggests the final letters.
The final letter of 'big' is 'g'.
'a'+'duo'='aduo'
'aduo' in reverse letter order is 'ouda'.
'ouda' put after 'g' is 'GOUDA'.
(Other definitions for gouda that I've seen before include "Dutch 4 across" , "It comes from Holland" , "Mild Dutch cheese" , "Round Dutch cheese" , "type of cheese" .)