Record of hospital department emergency room (5)
I believe the answer is:
enter
'record' is the definition.
(enter can mean to enter into a record)
'hospital department emergency room' is the wordplay.
'hospital department' becomes 'ENT' (Ear, Nose and Throat department).
'emergency room' becomes 'ER' (abbreviation popularized by US TV series).
'ent'+'er'='ENTER'
'of' acts as a link.
(Other definitions for enter that I've seen before include "Get in" , "Inscribe" , "Gain admission" , "Take part in a contest" , "Set foot in" .)