Charade (cryptic crossword)
A charade is a cryptic crossword device in which the answer is built by writing two or more separately clued pieces one after another, in order, with no letters moved, added or removed.
The name comes from the parlour game, where a word is acted out one syllable at a time and the audience assembles the whole from the parts. A cryptic charade works the same way: each fragment of the clue defines a short word or abbreviation, and you write them down in sequence.
The clue "Vehicle animal underfoot (6)" gives CARPET: CAR for vehicle, PET for animal, and underfoot as the definition. Setters signal the joining with words like on, with, after, before, by and next to. In a down clue, on and over can mean above rather than after, because the entry runs vertically.
What marks a charade out from the other devices is that nothing is disturbed. An anagram rearranges letters, a container hides one word inside another and a reversal turns letters backwards. A charade simply concatenates, which makes it the easiest device to spot once you know it exists and the hardest to see before that.