In Rome, one editor surplus to requirements (6)
I believe the answer is:
unused
'in' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'rome one editor surplus to requirements' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'un' (northern English dialect form of 'one') and 'un' is present in the answer.
'editor' could be 'ed' (abbreviation) and 'ed' is found within the answer.
The remaining letters 'us' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for unused that I've seen before include "In mint condition" , "hadn't been exploited" , "Unaccustomed" , "'Fresh, new (6)'" , "Mint, as new" .)