Musician in trio sang out of key? (8)
I believe the answer is:
organist
'musician' is the definition.
(I know that organist is a type of musician)
'trio sang out of key?' is the wordplay.
'trio sang' can be anagrammed to 'ORGANIST'.
Though, I'm unsure how the anagram is indicated.
'in' is the link.
Can you help me to learn more?
(Other definitions for organist that I've seen before include "One plays in church usually" , "It groans for church musician" , "Cathedral musician" , "Accompanist, keyboard player" , "Roasting (anag)" .)