The most common and most likely answer to this crossword clue is the 7 letter word CLUBBED
I've seen this crossword clue in Independent
C
L
U
B
B
E
D
Buddy explains!

The straight part
We know that "hit with staff" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hit with staff = clubbed.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 CLUBBED mean?
CLUBBED verb- To hit with a club.
- To join together to form a group.
- To combine into a club-shaped mass.
- To go to nightclubs.
- To pay an equal or proportionate share of a common charge or expense.
- To raise, or defray, by a proportional assessment.
- To drift in a current with an anchor out.
- To throw, or allow to fall, into confusion.
- To unite, or contribute, for the accomplishment of a common end.
- To turn the breech of (a musket) uppermost, so as to use it as a club.
- Shaped like a club; grasped like, or used as, a club.