With regard to something to be chewed over, editor concentrated (7)
I believe the answer is:
reduced
'concentrated' is the definition.
('reduce' can be a synonym of 'concentrate')
'with regard to something to be chewed over editor' is the wordplay.
'with regard' becomes 're'.
'to something to be chewed' becomes 'cud' (I've seen this before).
'over' shows that the letters should be reversed in order.
'editor' becomes 'ed'.
'cud' in reverse letter order is 'duc'.
're'+'duc'+'ed'='REDUCED'
(Other definitions for reduced that I've seen before include "Got rid of some bodily weight" , "Lowered in price" , "Lessened" , "Diminished - cut-price" , "Abridged" .)