For example, Tolkien enthusiast is overwhelmed by endless choice (9)
I believe the answer is:
fantasist
'for example tolkien enthusiast' is the definition.
I can't tell whether this definition defines the answer.
'is overwhelmed by endless choice' is the wordplay.
'overwhelmed by' is an insertion indicator (inserted letters get absorbed or overwhelmed).
'endless choice' becomes 'fantast' (I can't explain this - if you can you should believe this answer much more).
'is' placed within 'fantast' is 'FANTASIST'.
Can you help me to learn more?
(Other definitions for fantasist that I've seen before include "Creator of very imaginative fiction" , "Walter Mitty type?" , "Dreamer" .)