Repressed youngster ringing hospital department (4-2)
I believe the answer is:
pent-up
'repressed' is the definition.
(I know that repressed can be written as pent-up)
'youngster ringing hospital department' is the wordplay.
'youngster' becomes 'pup' (young dog).
'ringing' is an insertion indicator.
'hospital department' becomes 'ENT' (abbreviation for Ear, Nose and Throat department).
'pup' enclosing 'ent' is 'PENT-UP'.
(Other definitions for pent-up that I've seen before include "Dammed or repressed" , "Repressed, emotions say" , "Held back, confined" , "Confined like dam water or suppressed anger" , "Closely confined" .)