The most common and most likely answer to this crossword clue is the 6 plus 3 plus 6 letter word MORTAR AND PESTLE
M
O
R
T
A
R
A
N
D
P
E
S
T
L
E
More clues leading to the result MORTAR AND PESTLE
Buddy explains!
The straight part
We know that "Together they pound" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case together they pound = mortar and pestle.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.