The match that will take place at Tottenham's home ground is decisive because they can achieve a bigger victory if they are able to take advantage of the conditions. Tottenham did not play badly in the first leg, it's just that they were unable to create chances to score because even though they had several chances, Tottenham had problems in the finishing stage. The momentum of playing at home must be used by Tottenham and they must not take it easy if they don't work hard to get the win.
I also assume so because in the first leg Tottenham played with a higher level of ball possession and AZ Alkmaar only won because of one own goal so that it was just luck for the home team in the first leg. As for the second leg I think Tottenham will try with maximum ability in order to win with a higher score and be able to qualify for the next round to compete again in the last eight of the Europa League this season. And I am quite sure that Tottenham will not underestimate their opponents at home because being behind by one goal in the first leg is still quite possible for Tottenham to reply in the second leg.