The most common and most likely answer to this crossword clue is the 7 letter word GUNG-HO
I've seen this crossword clue in The Guardian
G
U
N
G
-
H
O
Buddy explains!

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 GUNG-HO mean?
GUNG-HO adjective- Overly enthusiastic or energetic.
- Cocky, undisciplined, contemptuous of rules