Scoundrel among performers with a bit of oomph is performer missing something (8)
I believe the answer is:
castrato
'oomph is performer missing something' is the definition.
I can't tell whether this definition defines the answer.
'scoundrel among performers with a bit' is the wordplay.
'scoundrel' becomes 'rat' (both can mean a dishonourable person).
'among' is an insertion indicator (inserted letters are placed among others).
'performers' becomes 'cast' (I've seen this before).
'with' says to put letters next to each other.
'a bit' becomes 'o' (resembles 0, a binary digit or bit).
'cast'+'o'='casto'
'rat' going inside 'casto' is 'CASTRATO'.
'of' is the link.
Can you help me to learn more?
(Other definitions for castrato that I've seen before include "Male singer operated on before puberty to retain his soprano voice" , "singer - he's missing something" , "Former high male singer" , "Emasculated male singer with a soprano or alto voice" , "Male singer with a high-pitched voice" .)