Possibly rising after nothing starts (7)
I believe the answer is:
origins
'starts' is the definition.
(I've seen this in another clue)
'possibly rising after nothing' is the wordplay.
'possibly' indicates anagramming the letters.
'after' says to put letters next to each other.
'nothing' becomes 'o' (O resembles 0).
'rising' with letters rearranged gives 'rigins'.
'rigins' after 'o' is 'ORIGINS'.
(Other definitions for origins that I've seen before include "Beginnings, ancestry" , "Beginnings, sources" , "Parentage" , "So I grin (anag.)" , "Lines of descent" .)