Happen to emerge embracing a sailor (4,5)
I believe the answer is:
come about
'happen' is the definition.
(synonyms)
'emerge embracing a sailor' is the wordplay.
'emerge' becomes 'comeout' (synonyms).
'embracing' is an insertion indicator.
'a sailor' becomes 'ab' (abbreviation for able seaman).
'comeout' placed around 'ab' is 'COME ABOUT'.
'to' acts as a link.
(Other definitions for come about that I've seen before include "Happen - to change course in yacht" , "turn?" .)