Delay retiring before a festive occasion (4)
I believe the answer is:
gala
'festive occasion' is the definition.
(thesaurus)
'delay retiring before a' is the wordplay.
'delay' becomes 'lag' (lag is a kind of delay).
'retiring' says the letters should be written backwards.
'before' is a charade indicator (letters next to each other).
'lag' reversed gives 'gal'.
'gal'+'a'='GALA'
(Other definitions for gala that I've seen before include "A show of charity" , "Public festivity" , "Sports meeting" , "Festive occasion - variety of apple" , "Festive entertainment" .)