It's for fighting delirium initially in hospital (4)
I believe the answer is:
ward
'hospital' is the definition.
(thesaurus)
'it's for fighting delirium initially' is the wordplay.
'it's for fighting' becomes 'war' (I've seen this in other clues).
'initially' suggests taking the first letters.
The first letter of 'delirium' is 'd'.
'war'+'d'='WARD'
'in' acts as a link.
(Other definitions for ward that I've seen before include "Minor with guardian - division of city" , "Hospital room with beds" , "zone for votes" , "Local administrative district" , "Old guard" .)