Altered damaged mechanism (7)
I believe the answer is:
treadle
'mechanism' is the definition.
'altered damaged' is the wordplay.
'damaged' is an anagram indicator.
'altered' anagrammed gives 'TREADLE'.
(Other definitions for treadle that I've seen before include "requires footwork" , "Foot lever giving power" , "Foot-operated lever" , "operate a spinning-wheel" , "Foot lever that works a machine" .)