Dishevelled attire one has to adjust (9)
I believe the answer is:
orientate
'to adjust' is the definition.
(I've seen this before)
'dishevelled attire one' is the wordplay.
'dishevelled' indicates anagramming the letters.
'attire'+'one'='attireone'
'attireone' with letters rearranged gives 'ORIENTATE'.
'has' acts as a link.
(Other definitions for orientate that I've seen before include "Get bearings, become accustomed to situation" , "Fix position" , "leave the West implicitly?" , "Become accustomed to new situation" , "determine position" .)