Bulgarian ruler's regimented fighters not in the country (5,10)

I believe the answer is:

urban guerrillas

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'bulgarian ruler's regimented fighters not in the country' is the definition.
I can't tell whether this definition defines the answer.

'bulgarian ruler's regimented fighters not in the country' is the wordplay.
'bulgarian ruler's' anagrams to 'URBAN GUERRILLAS'.
But, I am not sure how this is indicated.

Can you help me to learn more?

(Another definition for urban guerrillas that I've seen is " Terrorists".)

I've seen this clue in The Telegraph.

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