Southern sailor is a celebrity (4)
I believe the answer is:
star
'a celebrity' is the definition.
(I've seen this before)
'southern sailor' is the wordplay.
'southern' becomes 'S' (abbreviation).
'sailor' becomes 'tar' (slang term for a sailor).
's'+'tar'='STAR'
'is' acts as a link.
(Other definitions for star that I've seen before include "may be a dwarf or a giant" , "Five-pointed celestial body" , "Celeb" , "Famous actor" , "Celebrity in the world of entertainment" .)