Crossword Genius

For protective cover, she has 50lb (5)

Ross

I believe the answer is:

shell

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

'for protective cover' is the definition.
I can't judge whether this defines the answer.

'she has 50lb' is the wordplay.
'has' says to put letters next to each other.
'50lb' becomes 'll' (I can't explain this - if you can you should believe this answer much more).
'she'+'ll'='SHELL'

Can you help me to learn more?

(Other definitions for shell that I've seen before include "Petrol" , "Carapace; bombard" , "Mortar missile" , "cover" , "ammunition" .)

I've seen this clue in the Evening Standard.
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