Last letter nothing great (5)
I believe the answer is:
omega
'last letter' is the definition.
(last letter of the Greek alphabet)
'nothing great' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'great' becomes 'mega' (I've seen this in other clues).
'o'+'mega'='OMEGA'
(Other definitions for omega that I've seen before include "24th Greek letter" , "Last (Gk. letter)" , "end of series" , ""The Alpha and the ___"" , "character in Greek literature?" .)