A measure of what attracts concertgoers — tedious shows! (7)
I believe the answer is:
oersted
'a measure' is the definition.
(oersted is a kind of measure)
'attracts concertgoers tedious shows' is the wordplay.
'shows' indicates a hidden word.
'OERSTED' is hidden within 'attracts concertgoers tedious'.
'of what' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for oersted that I've seen before include "Physics unit of magnetic field strength" , "Physical unit" , "Ted Rose (anag) - Danish physicist who discovered electromagnetism" .)