Capital of the United Arab Emirates (3,5)
'capital of the united arab emirates' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for abu dhabi that I've seen before include "Asian capital" , "Part of UAE" , "Persian Gulf emirate" , "Largest member state of the UAE, and its capital" , "'UAE capital (3,5)'" .)
(Another definition for abudhabi that I've seen is " state".)