Do not change income, essentially, for backing groups (6)
I believe the answer is:
octets
'do not change income essentially for backing groups' is the definition.
I can't tell whether this defines the answer.
'change income essentially for backing groups' is the wordplay.
'change' is an anagram indicator.
'essentially' indicates the central letters.
'for backing' shows that the letters should be reversed in order.
'groups' becomes 'stet' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The middle of 'income' is 'co'.
'stet' backwards is 'tets'.
'co' anagrammed gives 'oc'.
'oc'+'tets'='OCTETS'
Can you help me to learn more?
(Other definitions for octets that I've seen before include "Groups of eight, often singers" , "Sets of eight" , "groups of eight, say singers" , "Groups of eight peformers" .)