An accident on court? (5)
I believe the answer is:
'an accident' is the definition.
(smash is a kind of accident)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for smash that I've seen before include "Overhead tennis shot" , "defeat" , "Break completely" , "Ruin; big (success)" , "Break like a glass or cup" .)