Some boatmen or seafarers from Scandinavia (5)
I believe the answer is:
norse
'from scandinavia' is the definition.
(I've seen this before)
'some boatmen or seafarers' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'NORSE' is hidden within 'boatmen or seafarers'.
(Other definitions for norse that I've seen before include "Viking" , "Old Scandinavian language" , "Relating to ancient Scandinavian" , "Relating to Norway" , "Ancient Scandinavian language" .)