Baltic, say, went ahead and shut (6)
I believe the answer is:
sealed
'shut' is the definition.
Both the definition and answer are adjectives. Perhaps there's an association between them I don't understand?
'baltic say went ahead' is the wordplay.
'baltic say' becomes 'sea' (baltic is a kind of sea).
'went ahead' becomes 'led' (led the way).
'sea'+'led'='SEALED'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for sealed that I've seen before include "Stamped as authentic" , "Closed tightly, maybe with wax" , "Closed (of lips, envelope, tomb etc)" , "Securely closed" , "Secured against leakage" .)