Here is a context clues worksheet on the noun contraption. Kids who have been read to as children very likely have heard and therefore understand this word; kids who haven’t enjoyed the benefits of nightly story time, and English language learners, probably have not. In any case, it is a word in common enough use in English that kids ought to know it.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.