The most common and most likely answer to this crossword clue is the 7 letter word BILLING
I've seen this crossword clue in The Daily Telegraph
B
I
L
L
I
N
G
More clues leading to the result BILLING
Buddy explains!
The straight part
We know that "Form of advertisement" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case form of advertisement = billing.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 BILLING mean?
BILLING verb- To dig, chop, etc., with a bill.
- To peck
- To stroke bill against bill, with reference to doves; to caress in fondness
- To advertise by a bill or public notice.
- To charge; to send a bill to.
- Amounts billed.
- Accounts receivable.
- The tracking of bills and amounts owed; the department within an institution or business that deals with the tracking of bills and amounts owed.
- The act or situation of including someone or something to those that make up a complete list.