Flask of cold wine knocked over (8)
I believe the answer is:
canister
'flask' is the definition.
(both are containers)
'cold wine knocked over' is the wordplay.
'cold' becomes 'c' (eg on taps).
'wine' becomes 'retsina' (type of Greek wine).
'knocked over' is a reversal indicator.
'retsina' reversed gives 'anister'.
'c'+'anister'='CANISTER'
'of' is the link.
(Other definitions for canister that I've seen before include "Tea-caddy" , "Metal storage container" , "Small metal container" , "Container for e.g. tea" , "Storage container, for tea say" .)