Maybe Rachel Riley's beginning to bore devoted fan (6)
I believe the answer is:
friend
'fan' 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?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for friend that I've seen before include "One you know well and regard with affection" , "Supporter of cause" , "Buddy, chum" , "allowed to pass by the guard" , "Close or intimate acquaintance" .)