Reduction as included in the order (8)
I believe the answer is:
decrease
'reduction' is the definition.
(I know that reduction can be written as decrease)
'as included in the order' is the wordplay.
'included in' is an insertion indicator.
'the order' becomes 'decree' (synonyms).
'as' placed inside 'decree' is 'DECREASE'.
(Other definitions for decrease that I've seen before include "Make or become less" , "Go down" , "Abate, diminish" , "drop" , "Reduction" .)