A classical author I'd nothing against at first (4)
I believe the answer is:
ovid
'a classical author' is the definition.
The definition suggests a singular noun which matches the answer.
'i'd nothing against at first' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'against' becomes 'v' (abbreviation for 'versus').
'at first' says to put letters next to each other.
'o'+'v'='ov'
'id' after 'ov' is 'OVID'.
Can you help me to learn more?
(Other definitions for ovid that I've seen before include "Latin poet (Ars amatoria, Metamorphoses)" , "Roman poet (Metamorphoses)" , "Metamorphoses author" , "Void for old Roman poet" , "Roman poet exiled by Augustus to Tomi on the Black Sea, where he died, AD 17" .)