When a draw-no-bet is involved in a parlay and the specific matchup ends in a draw, the whole bet is not affected. In this situation, the bet effectively becomes invalid and the sportsbook removes it from the parlay. This will however lead to a reduction in the expected payout.
A "draw no bet" or "tie no bet" in soccer betting is just what it sounds like you're betting a team to win, and if it ends in a draw, your bet will be refunded.