Spooner's old woman skewers seafood (5,5)

I believe the answer is:

stone crabs

I'm a little stuck... Click here to teach me more about this clue!

'spooner's old woman' is the definition.
I can't judge whether this definition defines the answer.

'skewers seafood' is the wordplay.
'skewers' becomes 'stone' (I can't explain this - if you can you should believe this answer much more).
'seafood' becomes 'crabs' (I've seen this in another clue).
'stone'+'crabs'='STONE CRABS'

Can you help me to learn more?

I've seen this clue in The Guardian.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.