The most common and most likely answer to this crossword clue is the 6 letter word LICKED
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More clues leading to the result LICKED
Buddy explains!

The straight part
We know that "defeated" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case defeated = licked.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 LICKED mean?
LICKED verb- To stroke with the tongue.
- To lap; to take in with the tongue.
- To beat with repeated blows.
- To defeat decisively, particularly in a fight.
- To overcome.
- To perform cunnilingus.
- To do anything partially.
- (of flame, waves etc.) To lap.