Sea creature mother has eaten somehow (7)
I believe the answer is:
manatee
'sea creature' is the definition.
(I've seen this before)
'mother has eaten somehow' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'has' says to put letters next to each other.
'somehow' is an anagram indicator.
'eaten' with letters rearranged gives 'natee'.
'ma'+'natee'='MANATEE'
(Other definitions for manatee that I've seen before include "Beast" , "rare sea mammal" , "To find sea cow" , "Sea cow - emanate (anag)" , "A neat me (anag) - large aquatic mammal" .)