Inference Clues force the reader to use rationale or  reasoning skills in order to figure out the meaning of an unknown word.  Even though the word is not directly defined, the reader can logically reason out the meaning using the information provided in the context.

Example:

No one ever believes that particular newspaper because it is famous for printing canards.

Why would anyone want to be an underachiever; he will never make good grades, never get a good job, and never be successful.