The incursion Dorian made (6)
I believe the answer is:
inroad
'the incursion' is the definition.
(inroad is a kind of incursion)
'dorian made' is the wordplay.
'made' is an anagram indicator.
'dorian' with letters rearranged gives 'INROAD'.
(Other definitions for inroad that I've seen before include "Offensive" , "Foray" , "Incursion, raid" , "Encroachment; hostile attack" , "One's intrusive" .)