It reflects political party seizing last opportunity to clean the mess in The House
I believe the answer is:
tidy up
'clean the mess in the house' is the definition.
I can't tell whether this defines the answer.
'it reflects political party seizing last opportunity' is the wordplay.
'reflects' is a reversal indicator.
'political party' becomes 'dup' (Democratic Unionist Party).
'seizing' is an insertion indicator.
'last' indicates one should take the final letters.
The last letter of 'opportunity' is 'y'.
'it' back-to-front is 'ti'.
'dup' placed around 'y' is 'dyup'.
'ti'+'dyup'='TIDY UP'
'to' is the link.
Can you help me to learn more?
(Other definitions for tidy up that I've seen before include "Make neater" , "Spring clean" , "Neaten" , "Make neat" , "Put (things or places) in order" .)