One having an L of a time passing a test? (6)
I believe the answer is:
driver
'one having an l of a time passing a test?' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is the entire clue.
Can you help me to learn more?
(Other definitions for driver that I've seen before include "Operator of a motor vehicle" , "Golf club for long shots" , "Member of RAC" , "chauffeuse" , "Motorist - golf club" .)