Occasion is cut short — that's not odd! (4)
I believe the answer is:
even
'that's not odd' is the definition.
('even' is the opposite to 'odd')
'occasion is cut' is the wordplay.
'occasion' becomes 'event' (I've seen this before).
'is cut' means to remove the last letter.
'event' with its last letter removed is 'EVEN'.
'short' is the link.
(Other definitions for even that I've seen before include "That's not odd" , "Late in the day" , "Not easily annoyed" , "Flush" , "Level, equal" .)