A name attached? Just the opposite (4)
I believe the answer is:
anon
'opposite' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'a name attached? just' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'attached? just' becomes 'on' (I've seen this in other clues. I am not sure about the 'just' bit.).
'a'+'n'+'on'='ANON'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for anon that I've seen before include "prolific author" , "Of unknown identity, in short" , "coming after a call" , "Presently - or unknown" , "soon to be written" .)