Salt flat around harbours (3)
I believe the answer is:
tar
'salt' is the definition.
(both can informally mean a sailor)
'flat around harbours' is the wordplay.
'harbours' indicates the answer is hidden within the clue.
'TAR' can be found hidden inside 'flat around'.
(Other definitions for tar that I've seen before include "Jack ..., British sailor" , "Informal name for sailor" , "Informal sailor or road-surfacing material" , "It paves the way" , "Thick, sticky liquid distilled from coal" .)