First of balls found in broken urinal behind entrance of tennis court (8)
I believe the answer is:
tribunal
'court' is the definition.
(I know that court can be written as tribunal)
'first of balls found in broken urinal behind entrance of tennis' is the wordplay.
'first of balls' becomes 'b' (1st letter of 'balls').
'found in' means one lot of letters goes inside another.
'broken' is an anagram indicator.
'behind' is a charade indicator (letters next to each other).
'entrance of' says to take the initial letters.
The first letter of 'tennis' is 't'.
'urinal'+'t'='urinalt'
'urinalt' is an anagram of 'triunal'.
'b' put inside 'triunal' is 'TRIBUNAL'.
(Other definitions for tribunal that I've seen before include "Court of arbitration - unlit bar (anag)" , "case" , "examination" , "Judgement seat" , "Special court" .)