Device that rocks cradle, with short wooden bar, not chromium (7)
I believe the answer is:
treadle
'device that rocks cradle with short wooden bar not chromium' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
This is the entire clue.
Can you help me to learn more?
(Other definitions for treadle that I've seen before include "Dear, let a foot lever emerge" , "Foot lever that works a machine" , "Foot-pedal" , "driving mechanism" , "Foot-operated lever" .)