The alteration having damaged, meant to repair the interior (9)
I believe the answer is:
amendment
'the alteration' is the definition.
(I've seen this before)
'damaged meant to repair the interior' is the wordplay.
'damaged' indicates anagramming the letters.
'to repair' becomes 'mend' (synonyms).
'the interior' is an insertion indicator.
'meant' anagrammed gives 'ament'.
'ament' enclosing 'mend' is 'AMENDMENT'.
'having' is the link.
(Other definitions for amendment that I've seen before include "Minor improvement" , "Statement added to or revising a document" , "the fifth one benefiting Uncle Sam's defendants?" , "Revision" , "Correction" .)