British vessel in bay (4)
I believe the answer is:
bark
'bay' is the definition.
(thesaurus)
'british vessel' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'vessel' becomes 'ark' (ark is a kind of vessel**).
'b'+'ark'='BARK'
'in' is the link.
(Other definitions for bark that I've seen before include "Outer covering of tree" , "Dog's sound" , "graze" , "craft" , "give sharp cry" .)