Offensive act not in fashion (7)

I believe the answer is:

outrage

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'offensive act' is the definition.
'outrage' can be an answer for 'act' (outrage is a kind of act). I am not sure about the 'offensive' bit.

'not in fashion' is the wordplay.
'not in' becomes 'out' ('out' is the opposite to 'in').
'fashion' becomes 'rage' (something all the rage is fashionable).
'out'+'rage'='OUTRAGE'

Can you help me to learn more?

(Other definitions for outrage that I've seen before include "Offend - atrocity" , "Gross violation of decency" , "Act that shocks public opinion, generates anger" , "Very angry reaction" , "Incense and offend" .)

I've seen this clue in The Telegraph.

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