Castle I'd destroyed, and fortresses (8)
I believe the answer is:
citadels
'fortresses' is the definition.
'castle i'd destroyed' is the wordplay.
'destroyed' indicates anagramming the letters.
'castle'+'id'='castleid'
'castleid' is an anagram of 'CITADELS'.
'and' acts as a link.
(Other definitions for citadels that I've seen before include "Dials etc up for fortresses" , "Keeps" , "Forts in cities for protection and refuge" , "Fortresses overlooking cities" , "Strongholds for shelter during battles" .)