The most common and most likely answer to this crossword clue is the 6 letter word INVENT
I've seen this crossword clue in Financial Times
I
N
V
E
N
T
More clues leading to the result INVENT
Buddy explains!

The straight part
We know that "Coin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case coin = invent.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 INVENT mean?
INVENT verb- To design a new process or mechanism.
- To create something fictional for a particular purpose.
- To come upon; to find; to discover.