Rightist sent out guards opposed to ancient ruler (11)

I believe the answer is:

constantine

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'ancient ruler' is the definition.
(Roman emperor)

'rightist sent out guards opposed' is the wordplay.
'rightist' becomes 'con' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'out' is an anagram indicator (out can mean wrong or inaccurate).
'guards' indicates putting letters inside (inserted letters are guarded).
'opposed' becomes 'anti' (similar in meaning).
'sent' anagrammed gives 'stne'.
'stne' going around 'anti' is 'stantine'.
'con'+'stantine'='CONSTANTINE'

'to' acts as a link.

Can you help me to learn more?

(Other definitions for constantine that I've seen before include "First Christian emperor" , "Great man" .)

I've seen this clue in The Times.

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