Night before always short (3)
I believe the answer is:
eve
'night before' is the definition.
(eve can mean the night before something)
'always short' is the wordplay.
'always' becomes 'ever' (synonyms).
'short' means to remove the last letter.
'ever' with its final letter taken off is 'EVE'.
(Other definitions for eve that I've seen before include "Night before an event" , "when it gets dark" , "Adam's partner" , "Previous day" , "Day before (an event)" .)