Main South Asian dish, curry principally (6)
I believe the answer is:
baltic
'main' is the definition.
(the main can mean the sea)
'south asian dish curry principally' is the wordplay.
'south asian dish' becomes 'balti' (dish from South Asia).
'principally' says to take the initial letters.
The first letter of 'curry' is 'c'.
'balti'+'c'='BALTIC'
(Other definitions for baltic that I've seen before include "Coming from Tallinn, perhaps" , "Near land-locked sea of Scandinavia" , "Near-landlocked sea of N Europe" , "The Sea around Scandinavia" , "cold waters" .)