Obsessive fan (4)
I believe the answer is:
stan
'obsessive fan' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for stan that I've seen before include "One of the comic duo" , "- Laurel, comedian" , "Laurel and Hardy, . . . . and Ollie" , "- Laurel, Hardy's partner" , "guy" .)