Damaged treadle may be changed (7)
I believe the answer is:
altered
'be changed' is the definition.
(similar in meaning)
'damaged treadle' is the wordplay.
'damaged' indicates an anagram.
'treadle' is an anagram of 'ALTERED'.
'may' acts as a link.
(Other definitions for altered that I've seen before include "Metamorphosed" , "Changed, adapted" , "Change" , "Treadle (anag)" , "Changed, modified" .)