… and not enthralled by countertenors (3)
I believe the answer is:
nor
'and not' is the definition.
('nor' means 'and also not')
'enthralled by countertenors' is the wordplay.
'enthralled by' says the answer is hidden in the clue.
'NOR' is hidden within 'countertenors'.
(Other definitions for nor that I've seen before include "Neither pairing" , "It's also not" , "Common conjunction, goes with neither" , "Negative conjunction" , "logic circuit" .)