A plan with merit? Not usually in this chamber (10)
I believe the answer is:
parliament
'this chamber' is the definition.
(as in a parliamentary chamber)
'a plan with merit? not usually' is the wordplay.
'with' says to put letters next to each other.
'not usually' is an anagram indicator (an unusual ordering of the letters).
'a'+'plan'+'merit'='aplanmerit'
'aplanmerit' anagrammed gives 'PARLIAMENT'.
'in' acts as a link.
(Other definitions for parliament that I've seen before include "The law is laid down here" , "Houses" , "Legislative assembly" , "UK legislature" , "Legislative body" .)