Eccentric loner was in the best position to be registered (8)
I believe the answer is:
enrolled
'be registered' is the definition.
(similar in meaning)
'eccentric loner was in the best position' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'loner' is 'enrol' which is located in the answer.
The remaining letters 'led' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'to' acts as a link.
Can you help me to learn more?
(Other definitions for enrolled that I've seen before include "Admitted" , "Registered as a participant" , "Officially registered" , "Registered as a member" , "Recruited; registered" .)