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Phrase(s): keep an ear to the ground [and] have an ear to the ground; keep one’s ear to the ground; have one’s ear to the ground
Fig. to devote attention to watching or listening for clues as to what is going to happen. • John had his ear to the ground, hoping to find out about new ideas in computers. • His boss told him to keep his ear to the ground so that he’d be the first to know of a new idea.
McGrawhill's American Idioms And Phrasal Verbs