Grins, having coal and gin prepared for festive event (5,7)
I believe the answer is:
Here is my best explanation:
'for festive event' is the definition.
I can't judge whether this definition defines the answer.
'grins having coal and gin prepared' is the wordplay.
'having' means one lot of letters go next to another.
'and' means one lot of letters go next to another.
'prepared' indicates anagramming the letters.
'grinscoalgin' anagrammed gives 'CAROL SINGING'.