Purpose of many a doctor's visit (4)
I believe the answer is:
exam
'purpose of many a doctor's visit' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for exam that I've seen before include "Something to sit" , "Scholastic test" , "Set of questions evaluating skill or knowledge, in short" , "End-of-course assessment" , "Formal knowledge test" .)