Quiet chat about reinforcement (5)
I believe the answer is:
patch
'reinforcement' is the definition.
(thesaurus)
'quiet chat about' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'about' indicates anagramming the letters.
'chat' anagrammed gives 'atch'.
'p'+'atch'='PATCH'
(Other definitions for patch that I've seen before include "Piece of cloth put on another" , "Mend with extra piece" , "Piece of material sewn over a hole" , "Plot - piece of cloth - period" , "Covering material" .)