Decreed a raid should be carried out by, one day (8)
I believe the answer is:
ordained
'decreed a raid' is the definition.
'ordained' can be an answer for 'decreed' (ordaining is a kind of decreeing). I'm not certain of the 'a raid' bit.
'carried out by one day' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'day' could be 'd' (abbreviation for day) and 'd' is found within the answer.
'carried' could be 'ran' ('run' can be a synonym of 'carry') and 'ran' is present in the remaining letters.
The remaining letters 'oed' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'should be' acts as a link.
Can you help me to learn more?
(Other definitions for ordained that I've seen before include "Decreed, or appointed to priesthood" , "Laid down the law" , "Conferred holy orders on" , "Like a priest" , "Elevated to the priesthood" .)