فَجَعَلَهُمْ جُذَاذًا (21:58) The word جُذَاذً is the plural for جُذَ. which means fragment or piece. Thus its meaning is that Sayyidna Ibrahim (علیہ السلام) broke the idols into small pieces.
إِلَّا كَبِيرًا لَّهُمْ (Save the big one of them - 21:58) That is, only the biggest idol was left intact and all the rest were broken. It is possible that the one which was left unbroken was either bigger in size or higher in esteem with the unbelievers.
لَعَلَّهُمْ إِلَيْهِ يَرْجِعُونَ (So that they may come back to him - 21:58) There can be three explanations to this expression. One, if the object of إِلَيْهِ (to him) is Sayyidna Ibrahim (علیہ السلام) then the meaning would be that he himself wanted the unbelievers to ask him why he had broken the idols which would give him a chance to sneer at them that what they worshipped could not even look after themselves. The second meaning of إِلَيْهِ يَرْجِعُونَ could be that he destroyed the idols in the hope that when the unbelievers saw them in pieces it might convince them of the futility of idol-worship and cause their return toward the religion of Sayyidna Ibrahim (علیہ السلام) . The third explanation is given by Kalbi. He says that the object of إِلَيْهِ is کَبِیر (the big). In that case the explanation would be that when the unbelievers, on their return saw the idols in pieces except the big one, who had a hammer resting on his shoulder, they might turn towards it for an explanation and getting no response from it they would see for themselves the helplessness of the idol.