Last letter of the Greek alphabet (5)
I believe the answer is:
omega
'last letter of the greek alphabet' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for omega that I've seen before include "Final outcome" , "Ending of a series or sequence" , "symbol of resistance?" , "long letter" , "Art of story-telling by body movement" .)