I arrive dishevelled in coastal region (7)
I believe the answer is:
riviera
'coastal region' is the definition.
(I've seen this before)
'i arrive dishevelled in' is the wordplay.
'dishevelled' is an anagram indicator.
'in' indicates putting letters inside.
'arrive' is an anagram of 'rivera'.
'i' inserted within 'rivera' is 'RIVIERA'.
(Other definitions for riviera that I've seen before include "Nice location" , "Coastal area between Italy and France" , "Warm coastal district" , "Mediterranean coastal region" , "Med coastal region" .)