The difference, the way I see it and emphasized, is that smart always implies intelligence, while clever does not (it implies that something is made in a way that is very effective; which can directly imply intelligence).

- smart (adj) = looking clean and neat; well dressed in fashionable and/or formal clothes: trông sạch sẽ, gọn gàng, ăn mặc hợp thời trang.

Ex: You look very smart in that suit.

- clever (adj) = quick at learning and understanding things: học hỏi nhanh và hiểu nhanh/ lanh lợi

- intelligent (adj) = good at learning, understanding and thinking in a logical way about things; showing this ability: học giỏi, hiểu nhanh, suy nghĩ logic về mọi thứ

=> clever = intelligent