Anger as first of referees at GAA exhibition .. (4)
I believe the answer is:
rage
'anger' is the definition.
(I know that rage is a type of anger)
'first of referees at gaa exhibition' is the wordplay.
'first of' says to take the initial letters.
The first letters of 'referees at gaa exhibition' is 'RAGE'.
'as' acts as a link.
(Other definitions for rage that I've seen before include "Mania" , "Uncontrolled anger" , "storm" , "Speak with great anger" , "Fury - fashion" .)