The most common and most likely answer to this crossword clue is the 9 letter word TOLERABLE
I've seen this crossword clue in Independent
T
O
L
E
R
A
B
L
E
More clues leading to the result TOLERABLE
- New role taken on by board is all right
- In list, over fifty parts adequate
- Mediocre line in Lear to be rewritten
- Mediocre, desolate bunch turned up with empty luggage
- It’s OK how the Spanish appreciate republican joining board
- Free beer to all? That’s not bad
- List including unlimited dance music, OK
- Board accepting revised role that is satisfactory …
- Adequate fare enhanced by new role
- Smashing ball or tee is not bad
Buddy explains!

The straight part
We know that "Mediocre" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mediocre = tolerable.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 TOLERABLE mean?
TOLERABLE adjective- Capable of being borne, tolerated or endured; bearable or endurable.
- Moderate in degree; mediocre; passable, acceptable or so-so.
- Such as to be tolerated or countenanced; permissible; allowable.
- In fair health; passably well.
- Tolerably; passably; moderately.