A flashing arrow is a type of emphasized foreshadowing, an audiovisual cue used in films and similar visual media to bring the attention of the audience to a particular object or situation, which will later be referred to or used in the advancement of plot.
[1] In an extreme example, it could literally be a flashing arrow pointing at the object, but the term is usually metaphorical, referring to visual focus and/or accompanying sound effects or music.
In the film Stranger than Fiction, the child with a bike and the bus driver appear in numerous scenes before both of them become a factor in Harold Crick's "death".
Another example is in the anime Ouran High School Host Club, where it is used repeatedly, for instance in the first episode, in which a flashing arrow and high-pitched beeping noise indicate a vase that a character breaks later in the scene.
With the more limited cinematic framing options of video games, the important object or clue may itself glow or flash to draw attention to it.