Bird, upright character, born on island (4)
I believe the answer is:
ibis
'bird' is the definition.
(ibis is a kind of bird)
'upright character born on island' is the wordplay.
'upright' shows that the letters should be reversed in order (in a down clue, letters go up).
'character' becomes 'i' ().
'born' becomes 'b' (abbreviation next to the year of someone's birth).
'on' means one lot of letters go next to another.
'island' becomes 'is' (abbreviation).
'i' put after 'b' is 'bi'.
'bi' backwards is 'ib'.
'ib'+'is'='IBIS'
(Other definitions for ibis that I've seen before include "Wading bird sacred to the Egyptians" , "Bird with long neck and legs and a curved bill" , "leggy bird" , "Large wader" , "may be sacred?" .)