The way to upset Dora (4)
I believe the answer is:
road
'the way' is the definition.
(road is a kind of way)
'upset dora' is the wordplay.
'upset' indicates anagramming the letters.
'dora' is an anagram of 'ROAD'.
'to' is the link.
(Other definitions for road that I've seen before include "motorway?" , "See 10" , "Mine passage; way" , "'The . . . . to hell is paved with good intentions'" , "Thoroughfare" .)