spanner in the works
English
Noun
spanner in the works (plural spanners in the works)
- (chiefly UK) Something that disrupts smooth operation or functioning.
- Synonyms: (US) wrench in the works, monkey wrench in the works
- The kids' involvement was unfortunately more of a spanner in the works than a helpful contribution toward Daddy's progress on the task, but he gamely pretended to be thankful anyway.