Supporter hit part of car's cooling system (3,4)
I believe the answer is:
fan belt
'part of car's cooling system' is the definition.
I can't judge whether this definition defines the answer.
'supporter hit' is the wordplay.
'supporter' becomes 'fan' (fan is a kind of supporter).
'hit' becomes 'belt' (belting is a kind of hitting).
'fan'+'belt'='FAN-BELT'
Can you help me to learn more?
(Other definitions for fan belt that I've seen before include "essential car component" , "Drive to car radiator cooler and alternator" , "Band in car driving alternator" , "Motor accessory" , "driver in engine" .)