Rejection of Conservative road leading to decay (3,3)
I believe the answer is:
dry rot
'decay' is the definition.
(I have seen 'Decay of timber ' mean 'dry rot' so perhaps 'decay' could also mean 'dry rot')
'rejection of conservative road leading' is the wordplay.
'rejection of' says the letters should be written in reverse.
'conservative' becomes 'tory' (I've seen this before).
'road' becomes 'rd' (abbreviation).
'leading' means one lot of letters go next to another.
'tory'+'rd'='toryrd'
'toryrd' written backwards gives 'DRY-ROT'.
'to' acts as a link.
(Other definitions for dry rot that I've seen before include "Decay of badly ventilated wood" , "domestic problem" , "Degeneration" , "housing problem?" , "Decay of wood poorly ventilated" .)