Eastern sea creature sheds tail in spring (7)
I believe the answer is:
emanate
'spring' is the definition.
(I've seen this before)
'eastern sea creature sheds tail' is the wordplay.
'eastern' becomes 'e'.
'sea creature' becomes 'manatee' (I've seen this before).
'sheds tail' means to remove the last letter (I've seen 'shed tail' mean this).
'manatee' with its last letter taken away is 'manate'.
'e'+'manate'='EMANATE'
'in' acts as a link.
(Other definitions for emanate that I've seen before include "Flow or proceed from" , "Give out, emit" , "Come out (of source)" , "spring" , "Issue or originate from manatee" .)