A key figure in the services (8)
I believe the answer is:
organist
'figure in the services' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'a key' is the wordplay.
I cannot really understand how this works, but
'a' could be 'an' and 'an' is located in the answer.
'key' could be 'g' (musical key) and 'g' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for organist that I've seen before include "It groans for church musician" , "Roasting (anag)" , "Accompanist, keyboard player" , "Church instr. player" , "One plays in church usually" .)