The most common and most likely answer to this crossword clue is the 3 plus 3 letter word TOP DOG
I've seen this crossword clue in The Times
T
O
P
D
O
G
More clues leading to the result TOP DOG
- Jumper put on setter, perhaps, the best one
- Almighty corporation set up for chief exec, say?
- Champion boxer possibly?
- Weed over my back, making a big noise
- Champion boxer perhaps?
- Winner, paid nothing, coming in to dress
- Big cheese Father with container served up
- The best setter
- Cruft’s Best In Show – Great Dane maybe
- Capo to kill boxer, perhaps
Buddy explains!
The straight part
We know that "leader of group" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leader of group = top dog.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.