Pick up body part by hospital (4)
I believe the answer is:
Here is my best explanation:
'pick up' is the definition.
(hearing is a kind of picking up)
'body part by hospital' is the subsidiary indication.
'body part' becomes 'ear' (ear is a kind of body part).
'by' says to put letters next to each other.
'hospital' becomes 'h'.
'ear' put after 'h' is 'hear'.
(Other definitions for hear that I've seen before include "Perceive with the ear", "Listen to", "Catch", "Perceive audibly", "Perceive aurally", "Find out", "Get wind of", "Pick up, aurally", "Perceive sound" and "Perceive by the auditory sense".)