IPA: /ˈklɛnʧər/
KK: /ˈklɛnʧər/
A tool or device that is used to grip or hold something tightly, often to prevent it from moving or being removed.
The carpenter used a clencher to secure the nails in place.
Clencher → It is formed from "clench" (from Middle English *clenchen*, meaning to grasp or grip) and "-er" (meaning a person who). A clencher is a person or thing that grips or holds tightly.
Think of someone who 'grips' tightly — that's what a clencher does, and the '-er' just means a person.