Tailless marine mammal from the Baltic? (3)
I believe the answer is:
sea
'the baltic?' is the definition.
(baltic is a kind of sea)
'tailless marine mammal' is the wordplay.
'tailless' means to remove the last letter.
'marine mammal' becomes 'seal' (I've seen this before).
'seal' with its last letter taken away is 'SEA'.
'from' acts as a link.
(Other definitions for sea that I've seen before include "Lesser ocean" , "The tide" , "that's easily reached from Dover?" , "Body of saltwater" , "eg Galilee" .)