One of those under the bed? (3)
I believe the answer is:
red
'bed?' is the definition.
The answer and definition can be both natural objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for red that I've seen before include "Colour for a blusher" , "- - poker: Kniphofia" , "could be a Marxist" , "Flushed" , "'If you see it, perhaps you're angry (3)'" .)