The most common and most likely answer to this crossword clue is the 5 letter word DUDES
I've seen this crossword clue in The Daily Telegraph
D
U
D
E
S
More clues leading to the result DUDES
- Men charge, capturing duke
- Guys, those failing to preserve energy
- . Useless opponents, city men on holiday?
- English in clothes for stylish people
- Stylish men expected to embrace daughter and son
- Guys overwhelmed by debts start to default
- Swells debts with old money invested
- American blokes investing energy in flops
- Head of entertainment invested in clothes and fancy dressers
- Sharp guys: failures with energy
Buddy explains!

The straight part
We know that "Swells" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case swells = dudes.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 DUDES mean?
DUDES noun- A man, generally a younger man.
- (used in the vocative) A term of address for someone, typically a man, particularly when cautioning him or offering him advice.
- An inexperienced cowboy.
- A tourist.
- A man who is very concerned about his dress and appearance; a dandy, a fop.
- To address someone as dude.
- To take a vacation in a dude ranch.
- Usually followed by up: to dress up, to wear smart or special clothes.