Lord to leave daughter (3)
I believe the answer is:
god
'lord' is the definition.
(the Lord means God)
'leave daughter' is the wordplay.
'leave' becomes 'go' (to go is to depart or leave).
'daughter' becomes 'd' (genealogical abbreviation).
'go'+'d'='GOD'
'to' acts as a link.
(Other definitions for god that I've seen before include "Pan perhaps" , "eg Cupid" , "Worshipped figure" , "Superhuman being" , "Mars or Mercury, say" .)