Seaman on his tod finds snail (7)
I believe the answer is:
abalone
'snail' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Maybe there's a link between them I don't understand?
'seaman on his tod' is the wordplay.
'seaman' becomes 'ab' (short for able seaman).
'on his tod' becomes 'alone' (to be on one's tod is to be alone).
'ab'+'alone'='ABALONE'
'finds' is the link.
Can you help me to learn more?
(Other definitions for abalone that I've seen before include "Source of mother-of-pearl" , "Edible marine mollusc -- Oban ale (anag)" , "something to eat from the sea" , "Edible shellfish, sea-ear" , "paua" .)