The most common and most likely answer to this crossword clue is the 5 plus 6 letter word COVER CHARGE
I've seen this crossword clue in The Times
C
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More clues leading to the result COVER CHARGE
- Insurance — attack sum added to bill
- Clubs ask too much, but those eating may have to pay it
- Clubs set too high a price for entrance fee
- It’s made by a restaurant chef originally at no more cost
- Clubs ask too much for entrance fee?
- Extra on the bill — cafe’s foremost swindle?
- Obscure to demand payment for entry into nightclub
Buddy explains!
The straight part
We know that "sum added to bill" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sum added to bill = cover 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.