Dorian's unreasonable encroachment (6)

I believe the answer is:

inroad

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

'encroachment' is the definition.
(I know that inroad is a type of encroachment)

'dorian's unreasonable' is the wordplay.
'dorian' can be anagrammed to 'INROAD'.
Though, I'm not sure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for inroad that I've seen before include "Incursion, raid" , "Foray" , "One's intrusive" , "Offensive" , "Ordain (anag.)" .)

I've seen this clue in the Evening Standard.

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