This sentence is grammatically correct, but it sounds awkward because of the construction “…in which you’ll see..”. It would be better written “Here’s the clip from CBS that features/includes Brad doing pull-ups”.

Using ‘which’ as a pronoun and preceding it with ‘in’ need not always result in sentences that sound wrong. For example, “The judge delivered a lengthy statement in which he highlighted many failings on the part of the company”.

My advice would be: if it sound wrong using ‘in which’, then just try alternative ways of saying the same thing.

Many sentences from our website sentencedict.com,hope helps:
1. Behavior is a mirror in which everyone shows his image.
2. Music is the only language in which you cannot say a mean or sarcastic thing.
3. Money is a bottomless sea, in which honour, conscience and truth may be drowned.
4. This was the diary in which Gina recorded her innermost thoughts and secrets.
5. You have a scant hour in which to pack.
6. The company is reconsidering the way in which it deploys its resources/staff.
7. In which direction are you going, north or south?
8. We’ve got to change the present system in which high court judges are regarded as somehow untouchable.
9. It is an event in which she reigns supreme.
10. It is a society in which homosexuality is rarely avowed.
11. The report criticizes the ham-fisted way in which complaints were dealt with.
12. The manner in which the decision was announced was extremely regrettable.
13. There is a famous Greek myth in which Icarus flew too near to the Sun.
14. Love is that condition in which the happiness of another person is essential to your own. Robert A. Heinlein
15. The female digs a pit in which to lay the eggs.

Your sentence is correct.

“in which” is a prepositional phrase used to refer to something you’ve already mentioned. Your sentence is one in which the phrase is used correctly.