I agree with Elliott Frisch that what you really want an answer from philosophy. The answer in *English word meaning*, that is, definitions, is easy. 

The definition of [intelligence](http://en.wikipedia.org/wiki/Intelligence) has changed throughout [history](http://en.wikipedia.org/wiki/Comparative_psychology) to reflect the attempt to *qualitatively* differentiate man from all animals. 
>Intelligence has been defined as one's capacity for logic, abstract thought, understanding, self-awareness, communication, learning, emotional knowledge, memory, planning, and problem solving. 

Music was thought to prove intelligence. It turns out animals can make music. Relatively recently, it was thought to be the ability to form a society. Ant and bee studies, as well as primate studies, knocked down that definition. Before Jane Goodall proved chimpanzees could use tools, the definition was the ability to use tools. Then it switched to language, which was shot down by Koko the gorilla's ability to use sign language effectively. It changes constantly. The ability to feel pain? Nonsense. Self-recognition? No good (many animals have a proven sense of self). Empathy? Nope (look at elephants, chimps, bonobos, etc.) Morality? Nope. We are left with the unprovable: spirituality, or a knowledge of mortality, or some other indefinable characteristic in animals. (Interestingly [this](http://www.dana.org/Cerebrum/Default.aspx?id=39196) article made a similar facile observation about young women.) Most honest neuroscientists today will tell you that the difference between animals and humans is a quantitative, not a qualitative, one. So the short answer is: intelligence exists in animals and humans.

Semantically, it depends entirely on a) your definitions of *intelligent* and *clever*, and b) *your* ability to comprehend higher order thinking and circular arguments.

[Clever](http://www.thefreedictionary.com/clever) is defined in several ways, two of which are  1. mentally bright; having sharp or quick intelligence; able, and 2. superficially skillful or witty; facile. If you set aside all the other meanings (agreeable, neat, amiable, etc.) it depends on which of the two major definitions for clever that you accept.

If clever = intelligent/bright, and intelligent = to use the power of reasoning and inference effectively, then **anything that is intelligent is clever**.

However, if by clever you mean facile (defined here as superficial; shallow: *a facile answer to a hard question*), then no, I don't think a dolphin can be facile, although there is plenty of evidence that they do have a sense of humor. They can also be amazingly emotionally aware. I saw a wild dolphin come to investigate a little girl on a boat after it had heard her singing. It stayed with her for about - it's hard to say, time is different when one is mesmerized - 10-15 minutes, then, before leaving, it very gently splashed *only her*. This was a *wild dolphin*.