A sea dog? (5)

I believe the answer is:

rover

'a sea dog?' is the definition.
(thesaurus)

This is the entire clue.

(Other definitions for rover that I've seen before include "Old scout" , "rambler" , "A vagrant" , "Pirate; dog's name" , "Wanderer, traveller" .)

I've seen this clue in the Evening Standard.

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