I wander up to a New Zealander (5)
I believe the answer is:
maori
'a new zealander' is the definition.
(the Maori are indigenous people of New Zealand)
'i wander up' is the wordplay.
'wander' becomes 'roam' (synonyms).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'i'+'roam'='iroam'
'iroam' written backwards gives 'MAORI'.
'to' acts as a link.
(Other definitions for maori that I've seen before include "Aborigine of New Zealand" , "NZ aboriginal" , "A native from the south" , "Native of New Zealand and the Cook Islands" , "antipodean language" .)