Extremely deceptive, my colour scheme (5)
I believe the answer is:
decor
'colour scheme' is the definition.
(I've seen this before)
'extremely deceptive my' is the wordplay.
'extremely' says to hollow out the word (remove centre letters).
'my' becomes 'cor' (both are expressions of surprise).
'deceptive' with its centre taken out is 'de'.
'de'+'cor'='DECOR'
(Other definitions for decor that I've seen before include "furnishings required" , "Interior design; stage scenery" , "Interior layout and furnishings" , "Interior colour scheme and furnishing" , "Style of furnishing etc used in room" .)