Charge round Pratt's Bottom in celebration (4)
I believe the answer is:
fete
'celebration' is the definition.
(I know that fete is a type of celebration)
'charge round pratt's bottom' is the wordplay.
'charge' becomes 'fee' (fee is a kind of charge).
'round' means one lot of letters goes inside another.
'bottom' suggests the final letters.
The final letter of 'pratt' is 't'.
'fee' going around 't' is 'FETE'.
'in' is the link.
(Other definitions for fete that I've seen before include "Celebrate; village fair" , "Outdoor gala" , "Event held to raise money" , "(Honour with) festivities" , "Village festival" .)