Hospital drama involving one organ (3)
I believe the answer is:
ear
'organ' is the definition.
(ear is a kind of organ)
'hospital drama involving one' is the wordplay.
'hospital drama' becomes 'er' ().
'involving' indicates putting letters inside.
'one' becomes 'a'.
'er' going around 'a' is 'EAR'.
(Other definitions for ear that I've seen before include "Fruiting head of a cereal" , "Lend one and listen" , "Corn seed-holder" , "Head of grain" , "Aural appendage" .)