Racing vehicle in church, a fun event (7)
I believe the answer is:
chariot
'racing vehicle' is the definition.
(historical vehicle)
'church a fun event' is the wordplay.
'church' becomes 'ch' (common abbreviation).
'fun event' becomes 'riot' (if something's a riot it's a lot of fun).
'ch'+'a'+'riot'='CHARIOT'
'in' acts as a link.
(Other definitions for chariot that I've seen before include "Ben Hur's car" , "'Two-wheeled, horse-drawn vehicle (7)'" , "Old vehicle (of fire?)" , "ceremonial carriage" , "coach" .)