Key slang for “snail” (8)
I believe the answer is:
escargot
'snail' is the definition.
(escargot means an edible snail)
'key slang' is the wordplay.
'key' becomes 'esc' ('Escape' key on a computer keyboard).
'slang' becomes 'argot' (synonyms).
'esc'+'argot'='ESCARGOT'
'for' acts as a link.
(Other definitions for escargot that I've seen before include "Edible snail (from Fr.)" , "One continually moving house" , "Cart goes carrying edible French snail" , "French delicacy" , "mollusc, from Paris" .)