The most common and most likely answer to this crossword clue is the 9 letter word OFFENBACH
I've seen this crossword clue in The Guardian
O
F
F
E
N
B
A
C
H
More clues leading to the result OFFENBACH
- Composer on holiday with another, eating nut
- Composer not keen on a pop screening please note
- Main city‘s much spoken of Welsh address
- Romantic composer in many cases sounded ahead of baroque composer
- One composer bringing endless distress to another
- Almost hurt the feelings of composer, German composer
- Composer frequently sounds like another
Buddy explains!

The straight part
We know that "Main city" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case main city = offenbach.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.