There's nothing left after half nine (3)
I believe the answer is:
nil
'there's nothing' is the definition.
(I've seen this before)
'left after half nine' is the wordplay.
'left' becomes 'L' (common abbreviation).
'after' is a charade indicator (letters next to each other).
'half' means to take half the letters.
'nine' cut in half is 'ni'.
'l' put after 'ni' is 'NIL'.
(Other definitions for nil that I've seen before include "Nothing, zero" , "Latin zero" , "Non-existent" , "Nothing, no value" , "Score of nought" .)