Ruin of Roman camp, say (9)
I believe the answer is:
devastate
'ruin' is the definition.
(devastating is a kind of ruining)
'roman camp say' is the wordplay.
'roman camp' becomes 'deva' (I can't justify this - if you can you should believe this answer much more).
'say' becomes 'state' ('state' can be a synonym of 'say').
'deva'+'state'='DEVASTATE'
'of' is the link.
(Other definitions for devastate that I've seen before include "Ruin" , "floor" , "Spoil" , "Destroy" , "Lay waste or overwhelm with grief" .)