Heads for Baltic after some Scandinavian fish (4)
I believe the answer is:
bass
'fish' is the definition.
(I've seen this before)
'heads for baltic after some scandinavian' is the wordplay.
'heads for' says to take the initial letters (I've seen 'head for' mean this).
The initial letters of 'baltic after some scandinavian' is 'BASS'.
(Other definitions for bass that I've seen before include "Performer" , "part of score" , "Very low - perch" , "Low singer" , "Lowest adult male singing voice" .)