Open bottle containing a French port (6)
I believe the answer is:
uncork
'open bottle' is the definition.
(I've seen this before)
'a french port' is the wordplay.
'a french' becomes 'un' ('a' in French).
'port' becomes 'cork' (I've seen this in other clues**).
'un'+'cork'='UNCORK'
'containing' acts as a link.
(Other definitions for uncork that I've seen before include "Clear a bottleneck" , "Open (Chablis, say)" , "Remove traditional stopper from wine bottle" , "Open (a wine bottle)" , "open tent?" .)