扬起 is a resultative verb compound (r.v.) where 扬 means 'lift, toss' and 起 adds an upward direction complement, together meaning 'to lift up, to raise into the air' — typically used for dust, sand, hair, or flags blowing upward, but also metaphorically for raising spirits or morale. Because the 起 complement is directional, the object that gets lifted usually follows the whole compound (扬起灰尘) or separates the two characters in some spoken contexts, though the compound form is common.