One who inherits after time what’s belonging to them (5)
I believe the answer is:
their
'belonging to them' is the definition.
(I've seen this before)
'one who inherits after time' is the wordplay.
'one who inherits' becomes 'heir' (I've seen this before).
'after' means one lot of letters go next to another.
'time' becomes 't'.
'heir' after 't' is 'THEIR'.
'what's' is the link.
(Other definitions for their that I've seen before include "Relating to them" , "Belonging to those people" , "Some would say his (or her)" , "Belonging to him (perhaps wrongly)" , "Possessive pronoun" .)