Destroy borders of Delaware and Virginia, say (9)
I believe the answer is:
devastate
'destroy' is the definition.
(devastating is a kind of destroying)
'borders of delaware and virginia say' is the wordplay.
'borders of' says to hollow out the word (remove centre letters).
'and' means one lot of letters go next to another.
'virginia' becomes 'va' (US state abbreviation).
'say' becomes 'state' ('state' can be a synonym of 'say'**).
'delaware' with its middle taken out is 'de'.
'de'+'va'+'state'='DEVASTATE'
(Other definitions for devastate that I've seen before include "Lay waste or totally crush" , "Spoil" , "Destroy" , "floor" , "Ruin" .)