Dead snail? (5)

I believe the answer is:

slain

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'dead' is the definition.
('slain' can be similar in meaning to 'dead')

'snail?' is the wordplay.
'snail' anagrams to 'SLAIN'.
However, I am unsure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for slain that I've seen before include "Violently killed" , "Put to the sword" , "Killed, murdered" , "Slaughtered" .)

I've seen this clue in the Evening Standard.

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