The most common and most likely answer to this crossword clue is the 5 letter word EFFED
I've seen this crossword clue in The Guardian
E
F
F
E
D
More clues leading to the result EFFED
- Used bad language very loudly in centre of Leeds
- Swore what Emirates official did’s not right
- Each foot initially grazed, swore
- Swore that Iron Duke supported serfs evenly
- Meat is served, be away and get cursed
- As per slang, doomed, affected badly; no act
- Used four-letter words - this don is strangely offended
Buddy explains!

The straight part
We know that "swore" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case swore = effed.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 EFFED mean?
EFFED verb- Fuck (the taboo swear word, but not in the sense "to copulate")