The most common and most likely answer to this crossword clue is the 6 letter word ISMAIL
I
S
M
A
I
L
Buddy explains!
The straight part
We know that "Merchant, film producer on a first-name basis" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case merchant, film producer on a first-name basis = ismail.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.