Relaxed time — unknown in TV hospital drama (8)
I believe the answer is:
casualty
'tv hospital drama' is the definition.
(I've seen this before)
'relaxed time unknown' is the wordplay.
'relaxed' becomes 'casual' (I've seen this before).
'time' becomes 't' (abbreviation).
'unknown' becomes 'y' (algebra).
'casual'+'t'+'y'='CASUALTY'
'in' is the link.
(Other definitions for casualty that I've seen before include "Victim - injured person" , "Person killed in accident or war" , "Someone killed or hurt" , "a person getting injured" , "Victim of accident or war" .)