The opening lead against 3NT is a diamond. North and South have 8 clubs between the two hands leaving just 5 for East and West. If declarer keeps playing clubs then, eventually, East and West will run out of them.
Declarer wins the opening lead and immediately plays a club, losing the trick. Upon regaining the lead, delcarer plays another club, again losing the trick. Once more, declarer regains the lead and plays a club. The defence have now won three club tricks but declarer has established the last club as a winner.
East had 3 clubs and West had 2. That's a 3-2 break but it doesn't always work out that way. When you're missing 5 cards the suit will sometimes break 4-1 or even 5-0. A 3-2 break will happen about 68% of the time. That's better than a finesse which will only work 50% of the time. Don't let a bad break now and then put you off!
Notice how important it is for declarer to play clubs immediately while there are still stoppers in the other suits even although it means losing the lead.
Losing the lead
Losing the lead just for the sake of losing the lead isn't going to help. Our aim is to establish extra tricks and we only want to lose the lead if that is indeed going to help. Lose the lead so that opponents run out of cards in a suit.
Losing the lead is much less painful if we're likely to get the lead back again! That's what we need aces and kings for. To get the lead back again. Provided we have can regain the lead later then we can be fearless losing the lead now.