Place below Arundel, crumbling over years (8)
I believe the answer is:
underlay
'place below' is the definition.
'arundel crumbling over years' is the wordplay.
'crumbling' indicates anagramming the letters.
'over' says to put letters next to each other.
'years' becomes 'y'.
'arundel' with letters rearranged gives 'underla'.
'underla'+'y'='UNDERLAY'
(Other definitions for underlay that I've seen before include "Support for carpet" , "flooring" , "it may be felt?" , "carpet protection" , "Felt or rubber beneath carpet" .)