Ray is mine! (5)
I believe the answer is:
shaft
I believe this clue is a double definition.
'ray' is the first definition.
(I know that ray can be written as shaft)
'is mine' is the second definition.
(I've seen this before)
(Other definitions for shaft that I've seen before include "Vertical passageway, into a mine say" , "Vertical mine access" , "An arrow or a mine passage" , "Ray (of sunlight)" , "Body of an arrow" .)