Couple jibe endlessly about average man in the street (3,6)
I believe the answer is:
joe public
'average man in the street' is the definition.
'couple jibe endlessly about' is the wordplay.
'endlessly' means to remove the last letter.
'about' indicates an anagram.
'couple'+'jibe'='couplejibe'
'couplejibe' with its last letter taken away is 'couplejib'.
'couplejib' with letters rearranged gives 'JOE PUBLIC'.
(Other definitions for joe public that I've seen before include "Man in the street" , "... and all those around him?" , "The general populace" .)