Waste a lot of time in prison (7)
I believe the answer is:
dungeon
'prison' is the definition.
(a dungeon is a prison cell)
'waste a lot of time' is the wordplay.
'waste' becomes 'dung' (dung is a kind of waste).
'a lot of time' becomes 'eon' (I've seen this in another clue).
'dung'+'eon'='DUNGEON'
'in' is the link.
(Other definitions for dungeon that I've seen before include "Eg, the Black Hole of Calcutta" , "old prison" , "prison the result" , "Place of confinement underground" , "Dark place of confinement" .)