The most common and most likely answer to this crossword clue is the 8 letter word ORIGINAL
I've seen this crossword clue in Financial Times
O
R
I
G
I
N
A
L
More clues leading to the result ORIGINAL
- Unusual exam covering one alcoholic drink
- Innovative start on Article 50
- Novel, not the translation
- Master one spirit during test
- Nothing in a girl’s novel is creative
- Novel said to encompass independent spirit
- First exam covers writer with spirit
- First exam includes one trap
- Regularly ignoring worrying sign, fault master
- Built an oil rig that’s not been done before
Buddy explains!

The straight part
We know that "master" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case master = original.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 ORIGINAL mean?
ORIGINAL noun- An object or other creation (e.g. narrative work) from which all later copies and variations are derived
- A person with a unique and interesting personality and/or creative talent
- An eccentric
- Relating to the origin or beginning; preceding all others
- First in a series or copies/versions
- Newly created
- Fresh, different
- Pioneering
- Having as its origin