Thomas is said to have a fan, it appears (7)
I believe the answer is:
phantom
'it appears' is the definition.
The definition suggests a singular noun which matches the answer.
'thomas is said to have a fan' is the wordplay.
I cannot really understand how this works, but
'thomas' could be 'tom' and 'tom' is found within the answer.
'a' could be 'an' and 'an' 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 phantom that I've seen before include "Illusion (at the opera?)" , "RR" , "Ballet-dancing costume" , "Spirit" , "Ghost of the Opera" .)