How strange that he's always short of a win! (6)
I believe the answer is:
victor
'how strange that he's always' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'short of a win' is the wordplay.
'short of' means to remove the last letter (I've seen 'shorter' mean this).
'a win' becomes 'victory' (a win is a victory).
'victory' with its final letter taken away is 'VICTOR'.
Can you help me to learn more?
(Other definitions for victor that I've seen before include "One coming out on top" , "The . . . . . . comic with Alf Tupper" , "The one who wins the battle" , "winning player" , "Conqueror" .)