Music producers unfortunately pain this group (7,6)
I believe the answer is:
upright pianos
'music producers' is the definition.
Although both the answer and definition are plural nouns, I cannot understand how they can define each other.
'unfortunately pain this group' is the wordplay.
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'pain'+'this'+'group'='painthisgroup'
'painthisgroup' anagrammed gives 'UPRIGHT PIANOS'.
Can you help me to learn more?
(Another definition for upright pianos that I've seen is " keyboard instruments".)