Crossword Genius

Unrehearsed concert put out, I am opening (9)

Ross

I believe the answer is:

impromptu

I'm a little stuck... Click here to teach me more about this clue!

'unrehearsed' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for impromptu that I've seen before include "With little or no preparation or forethought" , "Ad-lib" , "unrehearsed piece" , "Without much planning" , "Piano piece" .)

I've seen this clue in The Telegraph.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.