And initially Abbott had endless habit in UAE (3,5)
I believe the answer is:
abu dhabi
'habit in uae' is the definition.
The definition suggests a singular noun which matches the answer.
'and initially abbott had endless' is the wordplay.
I cannot really see how this works, but
an anagram of 'had' is 'dha' which is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for abu dhabi that I've seen before include "'UAE capital (3,5)'" , "Persian Gulf emirate" , "foreign land" , "Largest member state of the UAE, and its capital" , "Part of UAE" .)