Wren was one flying the Arctic (9)
I believe the answer is:
architect
'wren' is the definition.
(I've seen this before)
'one flying the arctic' is the wordplay.
'one flying' is an anagram indicator (letters fly around into new positions).
'the'+'arctic'='thearctic'
'thearctic' is an anagram of 'ARCHITECT'.
'was' acts as a link.
(Other definitions for architect that I've seen before include "Designer of buildings" , "Author" , "Building designer" , "Perhaps Scott" , "Wren perhaps" .)