British rescue vessel in bay (4)
I believe the answer is:
bark
'bay' is the definition.
(I've seen this before)
'british rescue vessel' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'rescue vessel' becomes 'ark' (I've seen this before).
'b'+'ark'='BARK'
'in' is the link.
(Other definitions for bark that I've seen before include "old vessel" , "Cri de cur?" , "A dog's shout" , "Dogs might react to this part of a tree" , "Animal sound - layer protecting tree trunk" .)