Bunion? Not something a tennis player wants to hear (4,5)
I believe the answer is:
foot fault
'not something a tennis player wants to hear' is the definition.
(a foot fault is against the rules in tennis)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for foot fault that I've seen before include "Bad service" , "twenty-six [ACHILLES HEEL] could be so described" .)