.... Enrico; about to ruin ours (6)
I believe the answer is:
caruso
'enrico' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see a link between them that I don't see?
'about to ruin ours' is the wordplay.
'about' becomes 'ca' (short for circa).
'to ruin' indicates anagramming the letters.
'ours' is an anagram of 'ruso'.
'ca'+'ruso'='CARUSO'
Can you help me to learn more?
(Other definitions for caruso that I've seen before include "Enrico . . . . . ., former tenor" , "songster" , "Classical tenor" , "Singer Enrico" , "Enrico ...... was famous Italian tenor" .)