Part of a lathe that could be altered (7)
I believe the answer is:
treadle
'part of a lathe that' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'could be altered' is the wordplay.
'could be' indicates anagramming the letters.
'altered' anagrammed gives 'TREADLE'.
Can you help me to learn more?
(Other definitions for treadle that I've seen before include "Machine foot-lever" , "Foot pedal for power" , "Rocking lever operated by foot" , "Foot lever that works a machine" , "Foot-operated lever" .)