The most common and most likely answer to this crossword clue is the 5 plus 7 plus 3 letter word SAINT BERNARD DOG
I've seen this crossword clue in The Guardian
S
A
I
N
T
B
E
R
N
A
R
D
D
O
G
Buddy explains!
The straight part
We know that "one that carries some?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one that carries some? = saint bernard 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.