Conservative member of the House of Lords rebuffed toady (5)
I believe the answer is:
creep
'toady' is the definition.
(thesaurus)
'conservative member of the house of lords rebuffed' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'member of the house of lords' becomes 'peer' (I've seen this before).
'rebuffed' shows that the letters should be reversed in order.
'peer' in reverse letter order is 'reep'.
'c'+'reep'='CREEP'
(Other definitions for creep that I've seen before include "wretch" , "Steal" , "Fawn" , "Move with stealth" , "Crawl; skulk" .)