Key frame? (8)
I believe the answer is:
skeleton
This might be a double definition.
'key' is the first definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'frame?' is the second definition.
(synonyms)
Can you help me to learn more?
(Other definitions for skeleton that I've seen before include "Minimum number required to keep things ticking over" , "Body-frame" , "Basic framework" , "Bare bones" , "set of bones?" .)