What type of figurative language is the FBI agent wore a wire during the undercover investigations

The correct answer is Alliteration.

Alliteration is derived from Latin's Latira which means 'letters of alphabet'. It is a stylistic device where number of words, having the same first consonant sound, appear close together.

It is used to emphasize something important that the writer or speaker would like to express.

Here, wore a wire is an alliteration as both wore and wire begin with the consonant w.

Using this device here makes the sentence appear more important in its meaning. It also makes the sentence sound better as the repetition of the w makes a very pleasant and continuous sound.