Just the night for play (7)
I believe the answer is:
twelfth
'just' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I can't see?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for twelfth that I've seen before include "for the night? Sort of" , "Ordinal number" , "day of parades" , "- - man (cricket)" , "Sewn join" .)