Cruel person lives in depressed time (6)
I believe the answer is:
sadist
'cruel person' is the definition.
(I've seen this before)
'lives in depressed time' is the wordplay.
'lives' becomes 'is' ('be' can be a synonym of 'live').
'in' is an insertion indicator.
'depressed' becomes 'sad'.
'time' becomes 't'.
'sad'+'t'='sadt'
'is' going inside 'sadt' is 'SADIST'.
(Other definitions for sadist that I've seen before include "An amalgam, made up of two or more parts" , "One deriving pleasure from inflicting pain on others" , "One enjoying hurting others" , "Tormentor" , "One who enjoys making others suffer" .)