Come out of aquatic mammal back to front (7)
I believe the answer is:
emanate
'come out of' is the definition.
'aquatic mammal back to front' is the wordplay.
I cannot really see how this works, but
'mammal' could be 'man' (man is a kind of mammal) and 'man' is present in the answer.
This explanation may well be incorrect...
(Other definitions for emanate that I've seen before include "Issue or originate from manatee" , "Issue forth, from a source" , "Come out (of source)" , "Give out, emit" , "Proceed or issue forth" .)