The most common and most likely answer to this crossword clue is the 12 letter word ACHIEVEMENTS
I've seen this crossword clue in The Times
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More clues leading to the result ACHIEVEMENTS
Buddy explains!
The straight part
We know that "Performances deemed very good?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case performances deemed very good? = achievements.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 ACHIEVEMENTS mean?
ACHIEVEMENTS noun- The act of achieving or performing; a successful performance; accomplishment
- A great or heroic deed or feat; something accomplished by valor or boldness
- An escutcheon or ensign armorial; now generally applied to the funeral shield commonly called hatchment.
- An award for completing a particular task or meeting an objective in a video game.
- (grammar) The lexical aspect (aktionsart) of verbs or predicates that change in an instant.