The most common and most likely answer to this crossword clue is the 9 letter word HAS-BEENS
I've seen this crossword clue in Financial Times
H
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S
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B
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More clues leading to the result HAS-BEENS
Buddy explains!
The straight part
We know that "they’re no longer effective" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they’re no longer effective = has-beens.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.
Crossword Answer definitions
HAS-BEENS noun- A person, especially one formerly popular or influential, who continues in their field after their popularity or effectiveness has peaked and is now in decline.