Aviator circles wood with more ostentation (8)
I believe the answer is:
flashier
'with more ostentation' is the definition.
(I've seen this before)
'aviator circles wood' is the wordplay.
'aviator' becomes 'flier' (synonyms).
'circles' is an insertion indicator.
'wood' becomes 'ash' (wood from an ash tree).
'flier' placed around 'ash' is 'FLASHIER'.
(Other definitions for flashier that I've seen before include "with more ostentation" , "more dazzling display" , "Showing more bravado" .)