"Nautical mile" confusing Emirati (8)
I believe the answer is:
maritime
'nautical' is the definition.
(synonyms)
'mile confusing emirati' is the wordplay.
'mile' becomes 'm' (common abbreviation).
'confusing' indicates anagramming the letters.
'emirati' with letters rearranged gives 'aritime'.
'm'+'aritime'='MARITIME'
(Other definitions for maritime that I've seen before include "beside the sea" , "Nautical" , "Coastal" , "Relating to the sea" , "Concerned with the main" .)