Clear round left one unconscious (9)
I believe the answer is:
Here is my best explanation:
'unconscious' is the definition.
'clear round left one' is the subsidiary indication.
'clear' becomes 'obvious' ('obvious' can be similar in meaning to 'clear'**).
'round' is an insertion indicator.
'left' becomes 'l' (common abbreviation).
'one' becomes 'i' (roman numeral).
'obvious' placed 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?".)