Set record -- first for a medical specialist! (11)
I believe the answer is:
radiologist
'a medical specialist' is the definition.
(radiologist is a kind of medical specialist)
'set record first' is the wordplay.
'set' becomes 'radio' (I've seen this before).
'record' becomes 'log' (logging is a kind of recording).
'first' becomes 'ist' (**).
'radio'+'log'+'ist'='RADIOLOGIST'
'for' is the link.
(Other definitions for radiologist that I've seen before include "Specialist in the use of X-rays" , "X-ray practitioner" , "X-ray expert" , "One working with X-rays" .)