The most common and most likely answer to this crossword clue is the 7 letter word DEALING
D
E
A
L
I
N
G
Buddy explains!

The straight part
We know that "doing business" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case doing business = dealing.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 DEALING mean?
DEALING verb- To distribute among a number of recipients, to give out as one’s portion or share.
- To administer or give out, as in small portions.
- To distribute cards to the players in a game.
- To pitch.
- To have dealings or business.
- To conduct oneself, to behave.
- To take action; to act.
- To trade professionally (followed by in).
- To sell, especially to sell illicit drugs.
- To be concerned with.
- To handle, to manage, to cope.
- (chiefly in the plural) A business transaction.
- One's manner of acting toward others; behaviour; interactions or relations with others.