Vessel containing giant bats in saline solution (10)
I believe the answer is:
brigantine
'vessel' is the definition.
(brigantine is a kind of vessel)
'giant bats in saline solution' is the wordplay.
'bats' is an anagram indicator (slang for mad).
'in' means one lot of letters goes inside another.
'saline solution' becomes 'brine' (brine is salty water).
'giant' is an anagram of 'igant'.
'igant' placed into 'brine' is 'BRIGANTINE'.
'containing' acts as a link.
(Other definitions for brigantine that I've seen before include "vessel" , "Boat" , "Two-masted sailing ship" .)