Kind of confinement (8)
I believe the answer is:
solitary
'kind of confinement' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for solitary that I've seen before include "Alone, single" , "Recluse" , "'Sole, lone (8)'" , "Lone; isolated" , "Existing alone" .)