Clear round left one unconscious (9)
I believe the answer is:
Here is my best explanation:
'unconscious' is the definition.
(I've seen this before)
'clear round left one' is the wordplay.
'clear' becomes 'obvious' (I've seen this before).
'round' is an insertion indicator.
'left one' becomes 'li' (left abbreviation plus 1).
'obvious' going around 'li' is 'OBLIVIOUS'.
(Other definitions for oblivious that I've seen before include "Unaware", "Totally unaware", "In ignorance", "Heedless", "Unconscious", "Blind (to)", "Ignorant", "Forgetful; unaware", "Apt to forget" and "totally in the dark?".)