As a result of this dissent you must make second billion (6)
I believe the answer is:
hereby
'as a result of this' is the definition.
(I've seen this before)
'dissent you must make second billion' is the wordplay.
I cannot quite understand how this works, but
'second' could be 're' (prefix meaning second in eg review, re-education) and 're' is found within the answer.
'billion' could be 'b' and 'b' is found in the answer.
The remaining letters 'hey' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hereby that I've seen before include "By this means, as result of this" , "(Formally) with this" , "By this means or act" , "Not far off" , "By means of this, legally speaking" .)