Where crossword puzzles are concerned, pragmatics can be viewed as the ability of the solver to interpret correctly the meaning or sense the constructor had in mind when writing a clue. When a clue appears as a single word without other words to give it a context, the puzzle itself can be thought of as the context. Oftentimes, even a multi-word clue can leave open more than one interpretation of the meaning or sense of the clue and this is part of the art of writing clues.
A constructor can intentionally use a vague expression in a clue to challenge the solver by not giving an appropriate amount of information. Ambiguities, too, are used in a similar way because the possible alternative denotations provide the challenge. With homonyms, it is specifically homographs that pose a problem to solvers because in written language they can not be distinguished without context, whereas homophones can. Polysemes are similarly problematic as they too have the same spelling for different senses of a word.
A perfect example of how a constructor can creatively mislead a solver even with some contextual information would be the homographic clue; bank deposit. The answer could be cash if the referenced bank is a financial institute or silt if the referenced bank is a river bank. An example of misleading with a one-word clue using a polysemic word is the clue; hire. The answer could be engage or employ. With both examples each possible answer has the same number of letters and each of the answers would be acceptable for the clue. It is in instances such as these that a solver must also take into consideration answers from the crossing clues in the grid to help them choose the best response.