Casual notice — wine in short supply (2,3)
I believe the answer is:
ad hoc
'casual' is the definition.
(ad hoc can mean unplanned or casual)
'notice wine in short supply' is the wordplay.
'notice' becomes 'ad' (both can mean an advertisement).
'wine' becomes 'hock' (hock is a kind of wine).
'in short supply' means to remove the last letter.
'hock' with its final letter taken off is 'hoc'.
'ad'+'hoc'='AD HOC'
(Other definitions for ad hoc that I've seen before include "... without preparation" , "(Of committee) formed for a single purpose" , "Intended for one specific matter" , "Applied to a particular situation" , "(Of group) formed for one purpose only" .)