The most common and most likely answer to this crossword clue is the 6 letter word AD-LIB
I've seen this crossword clue in Financial Times
A
D
-
L
I
B
More clues leading to the result AD-LIB
- Daughter engaged in excuse, mostly dreamt up on the spot
- A German tabloid points up unscripted remark
- Improvised excellent book about Donegal's borders
- One bald unexpected remark
- Improvised excellent book about Donegal’s borders
- Perform without notes from Brideshead librettist
- Improvised German newspaper article sent over
- Answer German paper back freely
- Impromptu pop-up taken to party once
- Extempore offering from well-read libertarian
Buddy explains!

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 AD-LIB mean?
AD-LIB verb- To improvise all or part of a speech or other performance, especially in comedy.