The most common and most likely answer to this crossword clue is the 6 letter word EFFETE
I've seen this crossword clue in Independent
E
F
F
E
T
E
More clues leading to the result EFFETE
- Exhausted, using energy on fine charity event
- Weak part of racket effective on return
- European female: fair, but decadent
- Spent summer in France just south of its capital, we hear
- Decadent European female at social function
- Degenerate English leader of Fascist party
- Swear that summer in Provence is precious
- Decadent English/French social function
- Weak passage from Genet effectively sent up
- Spent season in France with blind companion
Buddy explains!

The straight part
We know that "decadent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case decadent = effete.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 EFFETE mean?
EFFETE adjective- Of substances, quantities etc: exhausted, spent, worn-out.
- Lacking strength or vitality; feeble, powerless, impotent.
- Decadent, weak through self-indulgence.
- (of a person) Affected, overrefined