The most common and most likely answer to this crossword clue is the 3 plus 2 plus 6 letter word ACE OF HEARTS
I've seen this crossword clue in The Guardian
A
C
E
O
F
H
E
A
R
T
S
More clues leading to the result ACE OF HEARTS
Buddy explains!
The straight part
We know that "member of the pack" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case member of the pack = ace of hearts.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.