Unrivalled like the Commons? (8)
I believe the answer is:
peerless
'unrivalled' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for peerless that I've seen before include "superb" , "No Iolanthe performance could be so" , "Without equal, being without a lord?" , "Without equal, matchless" , "Excellent" .)