Rejection of Conservative road leading to decay (3,3)
I believe the answer is:
Here is my best explanation:
'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 subsidiary indication.
'rejection of' says the letters should be written backwards.
'conservative' becomes 'tory' (Tory is an example).
'road' becomes 'rd' (abbreviation).
'leading' means one lot of letters go next to another.
'toryrd' in reverse letter order is 'dryrot'.
'to' is the link.
(Other definitions for dry rot that I've seen before include "infestation", "Disease of wood not well ventilated", "Decay of wood not well ventilated", "housing problem?", "problem with deal?", "Decay of badly ventilated wood", "Fungus affecting wood", "Decay of wood poorly ventilated", "Wood decay" and "hidden decay".)