A couple excessively mentioned (3)
I believe the answer is:
two
'a couple' is the definition.
(I've seen this before)
'excessively mentioned' is the wordplay.
'excessively' becomes 'too' ('too' can be a synonym of 'excessively').
'mentioned' shows a homophone (sound like).
'too' is a homophone of 'TWO'.
(Other definitions for two that I've seen before include "Pair, deuce" , "not very many" , "1 + 1" , "One plus one" , "Number of Gentlemen of Verona" .)