Flashy clothing made insiders faint (7)
I believe the answer is:
shadowy
'faint' is the definition.
(I know that faint can be written as shadowy)
'flashy clothing made insiders' is the wordplay.
'flashy' becomes 'showy' (synonyms).
'clothing' is an insertion indicator (some letters cover up or clothe others).
'made insiders' becomes 'ad' (I am not sure about this - if you are sure you should believe this answer much more).
'showy' placed around 'ad' is 'SHADOWY'.
Can you help me to learn more?
(Other definitions for shadowy that I've seen before include "Mysterious" , "Obscure, dark" , "Obscure; dim" , "Why soda? (anag)" , "hazy" .)