Likely to see red snake in fancy (7)
I believe the answer is:
waspish
'likely to see red' is the definition.
'snake in fancy' is the wordplay.
'snake' becomes 'asp' (asp is a kind of snake).
'in' indicates putting letters inside.
'fancy' becomes 'wish'.
'asp' put into 'wish' is 'WASPISH'.
(Other definitions for waspish that I've seen before include "Pshaw, is like a stinging insect" , "Bad-tempered like stinging insect" , "Sharply irritable" , "Petulant" , "Spiteful (with a slender waist?)" .)