The most common and most likely answer to this crossword clue is the 6 letter word TIPPER
I've seen this crossword clue in The Daily Telegraph
T
I
P
P
E
R
Buddy explains!
The straight part
We know that "one generous to restaurant staff" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one generous to restaurant staff = tipper.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 TIPPER mean?
TIPPER noun- Someone who tips; someone who gives a gratuity.
- A small moustache.
- A goods vehicle with a tippable body, used for carrying loose materials such as gravel or rubble; a tipper truck or lorry.
- A device for loading goods such as coal by tipping them.
- One who gives private hints about racing or financial speculation, etc.; a tipster.
- (also in plural form) A cutting tool used to cut off or trim the horns of stock animals; a horn tipper.
- A kind of ale brewed with brackish water obtained from a particular well.