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 definition defines the answer.
'change income essentially for backing groups' is the wordplay.
'change' is an anagram indicator.
'essentially' indicates the central letters.
'for backing' is a reversal indicator.
'groups' becomes 'stet' (I can't explain this - if you can you should give a lot more credence to this answer).
The middle letters of 'income' are '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" .)