Like artillery dividing spoils in celebration (5,4)
I believe the answer is:
mardi gras
'celebration' is the definition.
(Mardi Gras is an example)
'like artillery dividing spoils' is the wordplay.
'like' becomes 'dig' (to dig can mean to appreciate or 'get').
'artillery' becomes 'RA' (Royal Artillery).
'dividing' indicates putting letters inside (inserted letters divide the word).
'spoils' becomes 'mars' ('mar' can be a synonym of 'spoil').
'dig'+'ra'='digra'
'digra' going inside 'mars' is 'MARDI GRAS'.
'in' acts as a link.
(Other definitions for mardi gras that I've seen before include "The lead up to fast" , "Revelry celebrating Shrove Tuesday" , "Carnival (day)" , "Time for carnival" , "pre-Lent festival" .)