Aquatic animal's tail appearing first in spring (7)
I believe the answer is:
emanate
'spring' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for emanate that I've seen before include "Issue or originate from manatee" , "Flow or proceed from" , "Issue or spread out from a source" , "Come forth" , "Proceed or issue forth" .)