Classics expert one can put in register (8)
I believe the answer is:
latinist
'classics' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'expert one can put in register' is the wordplay.
'expert one' becomes 'a' (a thing is one thing. I am not sure about the 'expert' bit.).
'can' becomes 'tin' (synonyms).
'put in' means one lot of letters goes inside another.
'register' becomes 'list' (listing is a kind of registering).
'a'+'tin'='atin'
'atin' going within 'list' is 'LATINIST'.
Can you help me to learn more?
(Other definitions for latinist that I've seen before include "I should understand the -um ending!" , "My specialist subject may be Ovid" , "language expert" .)