Court problem — ball out, feud developing (6,5)
I believe the answer is:
'court problem' is the definition.
The definition suggests a singular noun which matches the answer.
'ball out feud developing' is the wordplay.
'developing' indicates an anagram (letters developed into a new form).
'balloutfeud' is an anagram of 'DOUBLE-FAULT'.
Can you help me to learn more?
(Other definitions for double fault that I've seen before include "bad service again" , "evidence of poor service?" .)