Four in neat arrangement are indigenous (6)
I believe the answer is:
native
'indigenous' is the definition.
(similar in meaning)
'four in neat arrangement' is the wordplay.
'four' becomes 'IV' (Roman numerals).
'in' means one lot of letters goes inside another.
'arrangement' is an anagram indicator.
'neat' is an anagram of 'nate'.
'iv' placed within 'nate' is 'NATIVE'.
'are' acts as a link.
(Other definitions for native that I've seen before include "Indigenous person" , "Original inhabitant" , "Indigenous, aboriginal" , "Of person, belonging by birth to place" , "Belonging to a particular place by birth" .)