Ancient mariners snore terribly (5)

I believe the answer is:

norse

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'ancient mariners' is the definition.
(I've seen this in another clue)

I can't explain the remainder of the clue.

(Other definitions for norse that I've seen before include "These men were Vikings" , "Relating to ancient Scandinavian" , "Of old Scandinavia" , "Northern European" , "Language - senor! (anag)" .)

I've seen this clue in The Sun.

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