Crossword Genius

Sort of movement a crab displays (6)

Ross

I believe the answer is:

pincer

'crab displays' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Perhaps there's an association between them I don't understand?

I don't understand how the rest of the clue works.

(Other definitions for pincer that I've seen before include "Front claw" , "Crab's claw" , "Crab's nipper" , "Grasping limb of a crustacean" , "Claw, nipper" .)

I've seen this clue in The Times.
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