Left-leaning plot against Republican is in ruins (6)
I believe the answer is:
debris
'ruins' is the definition.
(I've seen this before)
'left-leaning plot against republican is' is the wordplay.
'left leaning plot' becomes 'deb' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'against' means one lot of letters go next to another.
'republican' becomes 'r' (abbreviation).
'deb'+'r'+'is'='DEBRIS'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for debris that I've seen before include "Rebids for rubble" , "Detritus, rubbish" , "Rubble as of fallen building" , "Scattered rubbish" , "Fragments of wreckage" .)