Adverbial phrase describing the way something is done or the state something is in, referring back to a previously mentioned manner.
そんな風に言わないでください。
Please don't say it like that.
彼はいつもそんな風に歩く。
He always walks in that manner.
Combination of the pre-noun adjectival そんな ('such') and the adverbial form of 風 (ふう, 'manner, way') with the particle に.