Destroy monarch with a heartless order (9)

I believe the answer is:

eradicate

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'destroy' is the definition.
(I've seen this before)

'monarch with a heartless order' is the wordplay.
'monarch with' becomes 'era' (I can't explain this - if you can you should give a lot more credence to this answer).
'a heartless' suggests removing the centre.
'order' becomes 'dictate' (synonyms).
'dictate' with its middle taken out is 'dicate'.
'era'+'dicate'='ERADICATE'

Can you help me to learn more?

(Other definitions for eradicate that I've seen before include "Scotch" , "Root out" , "Excise" , "Completely remove" , "Extinguish, wipe out" .)

I've seen this clue in The Independent and The Sun.

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