Crossword Genius

Decreed it should be under the dominion of (5)

Ross

I believe the answer is:

ruled

I'm a little stuck... Click here to teach me more about this clue!

'decreed' is the definition.
('rule' can be a synonym of 'decree')

'under the dominion of' is the wordplay.
I cannot quite see how this works, but
'dominion' could be 'rule' (synonyms) and 'rule' is found in the answer.
A single letter 'd' remains which might be clued in a way I don't see.
This explanation may well be incorrect...

'it should be' acts as a link.

Can you help me to learn more?

(Other definitions for ruled that I've seen before include "Governed or commanded" , "Governed - with lines" , "Made authoritative statement" , "Governed, used one's authority" , "with several lines" .)

I've seen this clue in the Evening Standard.
Want a hint initially instead of a full solution? Install my app