throw a spanner in the works Definition

spanner
noun

1. A metal hand tool that has an opening (sometimes an adjustable one) or various sizes of openings at one or both ends and which is used for gripping, tightening or loosening nuts, bolts, etc. US equivalent wrench noun 3

Idiom: a spanner in the works

A frustrating, annoying, irritating, etc person or thing.

Idiom: throw a spanner in the works (put, chuck etc a spanner in the works)

To frustrate, annoy, irritate, etc, especially by causing a plan, system, etc that is already in place to change.
Example: Harry's presence always puts a spanner in the works

Etymology: 18c: German, from spannen to unite or fasten.