The most common and most likely answer to this crossword clue is the 6 letter word SEVERS
I've seen this crossword clue in The Daily Telegraph
S
E
V
E
R
S
Buddy explains!

The straight part
We know that "docks" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case docks = severs.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.
What does SEVERS mean?
SEVERS verb- To cut free.
- To suffer disjunction; to be parted or separated.
- To make a separation or distinction; to distinguish.
- To disunite; to disconnect; to terminate.