Relative of swan confused with lion (3-2-3)
I believe the answer is:
son-in-law
'relative' is the definition.
(son-in-law is a kind of relative)
'swan confused with lion' is the wordplay.
'confused with' indicates anagramming the letters.
'swan' mixed up with 'lion' makes 'SON-IN-LAW'.
'of' acts as a link.
(Other definitions for son-in-law that I've seen before include "Relative by marriage" , "Member of extended family" , "He's married to your daughter" , "Daughter's husband" .)