The most common and most likely answer to this crossword clue is the 7 plus 6 letter word SERVICE CHARGE
I've seen this crossword clue in The Times
S
E
R
V
I
C
E
C
H
A
R
G
E
More clues leading to the result SERVICE CHARGE
- Perhaps tennis player’s run up part of restaurant bill
- Bill's extra procedure in court accusation
- Additional levy resulting from attack on fighting force
- What could be mass stampede for an addition to the menu?
- People waiting to receive this payment
- Strong stuff, including immorality with daily? It’ll go on the bill!
- Fill up after pre-MOT work? Bill may include it
- A restaurant may make this accusation after function
- Extra cost to pay as Army, say, goes on attack
- Mass accusation against restaurant practice
Buddy explains!
The straight part
We know that "Bill's extra" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bill's extra = service charge.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.