You could fall into a deep one (5)
I believe the answer is:
sleep
'you' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see an association between them that I don't see?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for sleep that I've seen before include "crash" , "''... that knits up the ravell'd sleeve of care'' (Macbeth)" , "Natural state of unconscious rest" , "Drop off" , "Slumber" .)