Cat - it destroyed loft (5)
I believe the answer is:
attic
'loft' is the definition.
(synonyms)
'cat it destroyed' is the wordplay.
'destroyed' is an anagram indicator.
'cat'+'it'='catit'
'catit' is an anagram of 'ATTIC'.
(Other definitions for attic that I've seen before include "Top storey" , "Loft room" , "Top apartment" , "Top chamber" , "where high-ups are found?" .)