The Query Tracer package can help you find out where a specific database query is being called. It works with both Clockwork and the Laravel Debugbar. Here's a screenshot taken from the readme:

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https://github.com/fitztrev/query-tracer

EDIT: turns out that Laravel Debugbar can do this out of the box:

https://twitter.com/barryvdh/status/732570607058046977