Argue about origin of native tree (5)
I believe the answer is:
rowan
'tree' is the definition.
(rowan tree is a kind of tree)
'argue about origin of native' is the wordplay.
'argue' becomes 'row'.
'about' becomes 'a' (abbreviation in Chambers**).
'origin of' suggests taking the first letters.
The initial letter of 'native' is 'n'.
'row'+'a'+'n'='ROWAN'
(Other definitions for rowan that I've seen before include "Tree - archbishop" , "Atkinson or Williams" , "ash native to mountain regions" , "Man" , "Mountain ash (at Lambeth!)" .)