Lover's knot, it's said (4)
I believe the answer is:
beau
'lover's' is the definition.
(beau is a kind of lover)
'knot it's said' is the wordplay.
'knot' becomes 'bow' (bow is a kind of knot).
'it's said' shows a homophone (sound like).
'bow' is a homophone of 'BEAU'.
(Other definitions for beau that I've seen before include "Admirer; fop, dandy" , "French boyfriend" , "An old boy friend like Brummel?" , "An old dandy like Brummel" , "Male admirer; dandy" .)