Son embraced by mother and mentor (6)
I believe the answer is:
master
'mentor' is the definition.
(thesaurus)
'son embraced by mother' is the wordplay.
'son' becomes 's'.
'embraced by' means one lot of letters goes inside another.
'mother' becomes 'mater' (old-fashioned term for mother).
's' inserted inside 'mater' is 'MASTER'.
'and' is the link.
(Other definitions for master that I've seen before include "The boss" , "Gain control of (something)" , "One has consummate skill" , "Skilled practitioner" , "Male teacher or ship's captain" .)