Heartless braggart and sailor (6)
I believe the answer is:
boater
'sailor' is the definition.
(synonyms)
'heartless braggart' is the wordplay.
'heartless' suggests removing the centre.
'braggart' becomes 'boaster' (synonyms).
'boaster' with its middle removed is 'BOATER'.
'and' is the link.
(Other definitions for boater that I've seen before include "(Of exercise) improving oxygen intake" , "Stiff hat made of straw" , "one going in the junk?" , "Hat style" , "Sailor's straw hat" .)