A delay set back the celebrations (4)
I believe the answer is:
gala
'a delay set back the celebrations' is the definition.
I can't tell whether this definition defines the answer.
'a delay set back' is the wordplay.
'delay' becomes 'lag' (lag is a kind of delay).
'set back' says the letters should be written backwards.
'a'+'lag'='alag'
'alag' reversed gives 'GALA'.
Can you help me to learn more?
(Other definitions for gala that I've seen before include "Festive performance" , "fair" , "Public party" , "A show of charity" , "Carnival, celebration" .)