Where to Find and Catch Clauncher
From Pokemon Go Wiki
Clauncher are found and captured in Nest and Habitat locations.
Nests
Clauncher Nests are locations that consistently spawn Clauncher.
Habitats
Clauncher Habitats are spawn locations where Clauncher is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: