Hospital doctor principally employing this form of communication (8)
I believe the answer is:
internet
'form of communication' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'hospital doctor principally employing this' is the wordplay.
'hospital doctor' becomes 'intern' (trainee doctor).
'principally' indicates taking the first letters.
The first letters of 'employing this' is 'et'.
'intern'+'et'='INTERNET'
Can you help me to learn more?
(Other definitions for internet that I've seen before include "Here, blogs" , "International computer-based network" , "Computer service" , "What could be offered at some cafes" , "The computer web" .)