The most common and most likely answer to this crossword clue is the 10 letter word COLLIERIES
I've seen this crossword clue in Financial Times
C
O
L
L
I
E
R
I
E
S
Buddy explains!

The straight part
We know that "pits" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pits = collieries.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.
Crossword Answer definitions
COLLIERIES noun- An underground coal mine, together with its surface buildings.
- A facility that supplies coal.