This may stop one from getting off (8)
I believe the answer is:
insomnia
'this may stop' is the definition.
The answer and definition can be both states of affairs as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for insomnia that I've seen before include "Habitual inability to sleep (8)" , "problem at night" , "Condition affecting sleep" , "In restless state" , "State of chronic sleeplessness" .)