A delay cuts back the celebration (4)
I believe the answer is:
gala
'the celebration' is the definition.
(gala is a kind of celebration)
'a delay cuts back' is the wordplay.
'delay cuts' becomes 'lag' (I can't explain this - if you can you should give a lot more credence to this answer).
'back' shows that the letters should be reversed in order.
'a'+'lag'='alag'
'alag' written backwards gives 'GALA'.
Can you help me to learn more?
(Other definitions for gala that I've seen before include "field day" , "Festive occasion - variety of apple" , "Special festivity" , "Special sports event" , "Special social or sporting occasion" .)