Strong backing needed for this sports-day event? (3-2-3)
I believe the answer is:
tug-of-war
'event?' is the definition.
(tug-of-war is a kind of event)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for tug-of-war that I've seen before include "Contest of strength" , "Pulling contest" , "Sporting test of strength" .)