Harsh call by the way to split a medical department (10)
I believe the answer is:
astringent
'harsh' is the definition.
(harsh can mean astringent or severe)
'call by the way to split a medical department' is the wordplay.
'call by' becomes 'astringe' (I can't justify this - if you can you should believe this answer much more).
'the way' becomes 'e' (Compass direction - East).
'to split' suggests deleting specific letters.
'a medical department' becomes 'ENT' (abbreviation for Ear, Nose and Throat department).
'ent' with 'e' taken out is 'nt'.
'astringe'+'nt'='ASTRINGENT'
Can you help me to learn more?
(Other definitions for astringent that I've seen before include "Sharp or severe in manner" , "medical preparation" , "Lotion" , "Scathing" , "description of wine?" .)