Legacy has to exist with the hunt (7)
I believe the answer is:
bequest
'legacy' is the definition.
(bequest is a kind of legacy)
'exist with the hunt' is the wordplay.
'exist' becomes 'be' (synonyms).
'with' means one lot of letters go next to another.
'the hunt' becomes 'quest' (quest is a kind of hunt).
'be'+'quest'='BEQUEST'
'has to' is the link.
(Other definitions for bequest that I've seen before include "Gift left in will" , "Something left in a will (7)" , "Gift by will of personal property" , "Endowment, legacy" , "Something gifted in a will" .)