Old director general punches where it hurts (5)
I believe the answer is:
reith
'old director general' is the definition.
The definition suggests a singular noun which matches the answer.
'punches where it hurts' is the wordplay.
'REITH' is hidden within the letters.
But, I'm not sure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for reith that I've seen before include "One put in charge of the BBC" , "broadcasting pioneer" , "BBC's first Director-General, d. 1971" , "Lord -, first BBC DG" , "BBC - Lectures, named for former DG" .)