The most common and most likely answer to this crossword clue is the 11 letter word SECOND-RATE
I've seen this crossword clue in The Guardian
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More clues leading to the result SECOND-RATE
Buddy explains!
The straight part
We know that "just not good enough" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case just not good enough = second-rate.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 SECOND-RATE mean?
SECOND-RATE noun- A British ship-of-the-line sail warship having 90 to 98 guns dispersed on three gundecks.
- Of mediocre quality; not first class.