expression, godan verb (-ru)
step aside; move to the side
Used when someone physically moves out of the way, often to let someone pass or to avoid being in the center. The expression is somewhat literary or formal, and 傍ら (かたわら) itself is a somewhat old-fashioned word for 'side'.
彼は道を譲るために傍らに寄った。
He stepped aside to give way.
More common and neutral way to say 'step aside'. 傍らに寄る is more literary and less frequent in everyday speech.
The expression combines 傍ら (かたわら, 'side') with 寄る (よる, 'to approach, draw near'). The exact historical derivation is uncertain, but it follows a standard pattern of noun + に + verb.