The most common and most likely answer to this crossword clue is the 8 letter word THUNDERS
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Buddy explains!

The straight part
We know that "Yells" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case yells = thunders.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does THUNDERS mean?
THUNDERS noun- The loud rumbling, cracking, or crashing sound caused by expansion of rapidly heated air around a lightning bolt.
- A deep, rumbling noise resembling thunder.
- An alarming or startling threat or denunciation.
- The discharge of electricity; a thunderbolt.
- The spotlight.
- To produce thunder; to sound, rattle, or roar, as a discharge of atmospheric electricity; often used impersonally.
- To make a noise like thunder.
- To talk with a loud, threatening voice.
- To say (something) with a loud, threatening voice.
- To produce something with incredible power