Clonks is a word with no antonyms as it is a slang term that is not used in formal vocabulary. The word "clonk" generally refers to a loud thud or deep, resonant sound. It is often used to describe the sound of heavy objects hitting each other, like the sound of a metal sheet falling on the ground or the sound of large rocks being pounded together. As it is a colloquial and informal term, there are no direct antonyms for it. One may use other words such as "click" or "ping" to convey a contrasting sound. Overall, clonks is a unique and expressive term that is best understood in context.