About to enter hospital for medical examination (4)
I believe the answer is:
scan
'medical examination' is the definition.
(I've seen this before)
'about to enter hospital' is the wordplay.
'about' becomes 'c' (abbreviation for circa).
'to enter' indicates putting letters inside.
'hospital' becomes 'san' (I've seen this before).
'c' inserted into 'san' is 'SCAN'.
'for' acts as a link.
(Other definitions for scan that I've seen before include "Look over (in order to copy?)" , "Examine carefully" , "Study the metre" , "at one's feet?" , "Glance at quickly rather than thoroughly" .)