Such keys perhaps best left in cupboards? (9)
I believe the answer is:
skeletons
'cupboards?' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Perhaps they are linked in a way I don't understand?
'such keys perhaps best left' is the wordplay.
I cannot quite understand how this works, but
'left' could be 'l' (common abbreviation) and 'l' is found within the answer.
'keys' could be 'ee' (the musical key E written twice) and 'ee' is located in the remaining letters.
This explanation may well be incorrect...
'in' is the link.
Can you help me to learn more?
(Other definitions for skeletons that I've seen before include "Lost knees (anag.)" , "Frameworks of bone" , "Bony frameworks" , "Frames of bodies" , "Body frames" .)