The most common and most likely answer to this crossword clue is the 6 letter word PINCER
I've seen this crossword clue in The Guardian
P
I
N
C
E
R
More clues leading to the result PINCER
Buddy explains!
The straight part
We know that "part of a king crab" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part of a king crab = pincer.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 PINCER mean?
PINCER noun- Any object that resembles one half of a pair of pincers.
- (sometimes figurative) To surround with a pincer attack.