Gaudy insect circling tree (6)
I believe the answer is:
flashy
'gaudy' is the definition.
('flashy' can be a synonym of 'gaudy')
'insect circling tree' is the wordplay.
'insect' becomes 'fly' (fly is a kind of insect).
'circling' means one lot of letters goes inside another (circling can mean going around or containing).
'tree' becomes 'ash' (ash is a kind of tree).
'fly' enclosing 'ash' is 'FLASHY'.
(Other definitions for flashy that I've seen before include "Tastelessly showy" , "Loud" , "Vulgar" , "Cheap and ostentatious" , "Garish" .)