Charge hospital department over decay (7)
I believe the answer is:
entrust
'charge' is the definition.
(I've seen this before)
'hospital department over decay' is the wordplay.
'hospital department' becomes 'ENT' (abbreviation for Ear, Nose and Throat department).
'over' says to put letters next to each other.
'decay' becomes 'rust' (rusting is a kind of decaying).
'ent'+'rust'='ENTRUST'
(Other definitions for entrust that I've seen before include "Give for safekeeping" , "Place in someone's 22 ac" , "Nutters (anag)" , "Assign (a responsibility to someone)" , "Consign" .)