Some animals pong, especially sea creatures (7)
I believe the answer is:
sponges
'creatures' is the definition.
(sponge is a kind of creature)
'some animals pong especially sea' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'SPONGES' can be found hidden inside 'animals pong especially sea'.
(Other definitions for sponges that I've seen before include "Cadges like sea animal" , "Primitive, porous, marine animals" , "heavy drinkers" , "Light, highly absorbent skeletons of marine animals" , "Cakes" .)