Told nine off for being idle (8)
I believe the answer is:
indolent
'idle' is the definition.
(similar in meaning)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for indolent that I've seen before include "Lazy, disinclined to work" , "Lazy, slothful" , "Disinclined to exert oneself" , "Disinclined to exertion or work" , "not willing to work" .)