Rump parliament's ultimate disastrous denial (4,3)
I believe the answer is:
tail end
'rump' is the definition.
('tail end' can be a synonym of 'rump')
'parliament's ultimate disastrous denial' is the wordplay.
'ultimate' says to take the final letters.
'disastrous' indicates an anagram.
The final letter of 'parliament' is 't'.
'denial' anagrammed gives 'ailend'.
't'+'ailend'='TAIL-END'
(Other definitions for tail end that I've seen before include "Very last part" , "Last batsmen" , "Hindmost part" , "Back" , "like late Charlie?" .)