Having lowered the tone like this, poor Ovett heartlessly tormented Coe (5,4)
I believe the answer is:
sotto voce
'having lowered the tone' is the definition.
I can't judge whether this definition defines the answer.
'like this poor ovett heartlessly tormented coe' is the wordplay.
'like this' becomes 'so'.
'poor' indicates anagramming the letters.
'heartlessly' says to hollow out the word (remove centre letters).
'tormented' is an anagram indicator.
'ovett' with its centre taken out is 'ovtt'.
'ovtt' is an anagram of 'ttov'.
'coe' anagrammed gives 'oce'.
'so'+'ttov'+'oce'='SOTTO VOCE'
Can you help me to learn more?
(Other definitions for sotto voce that I've seen before include "(Said) quietly" , "on the quiet" , "Like subdued talking" , "Speaking quietly" , "In an undertone, from Italian" .)