The most common and most likely answer to this crossword clue is the 5 plus 5 letter word GRAND PIANO
I've seen this crossword clue in The Daily Telegraph
G
R
A
N
D
P
I
A
N
O
More clues leading to the result GRAND PIANO
- GP wants extensive treatment for Joanna
- Super-soft one getting tickled?
- GP that’s highly-strung?
- GP’s instrument?
- One’s played God swiping last of Martini in knees-up for seniors?
- £1,000 mislaid in a potty, outside
- Good money Scotsman placed in Post Office — sound investment?
- King, along with pawn on rook’s square, held up major feature of key play?
- Concert instrument that’s flat
- Joanna is quiet after August
Buddy explains!

The straight part
We know that "Joanna" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case joanna = grand piano.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.