The most common and most likely answer to this crossword clue is the 7 letter word TRADING
I've seen this crossword clue in The Daily Telegraph
T
R
A
D
I
N
G
More clues leading to the result TRADING
- Start of terrible hullabaloo in newspaper business
- This kind of business requires grit and work
- Business given publicity in Herts town
- I rush the wrong way — no good for commercial activity
- Move quickly up in government’s primary dealing
- A day in Herts town doing business
- Marketing grant disbursed, including many inaugural incentives
- Daughter in coach finally organising buying and selling
- Nearly trick chess champion, making exchanges
- Traffic no good, I run in reverse on the left
Buddy explains!

The straight part
We know that "commercial activity" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case commercial activity = trading.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 TRADING mean?
TRADING verb- To engage in trade.
- To be traded at a certain price or under certain conditions.
- To give (something) in exchange for.
- To give someone a plant and receive a different one in return.
- To do business; offer for sale as for one's livelihood.
- To have dealings; to be concerned or associated (with).
- The carrying on of trade.
- Carrying on trade or commerce; engaged in trade.
- Frequented by traders.
- Venal; corrupt; jobbing.