Intermediary doesn't get airtime, despite having knowledge about niche subject (5)
I believe the answer is:
nerdy
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for nerdy that I've seen before include "Boringly studious" , "Bright but socially inept" , "Geeky" , "obsessive" .)