Marine creature with stinging tentacles (9)
I believe the answer is:
jellyfish
'marine creature with stinging tentacles' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for jellyfish that I've seen before include "Sea animal with stinging tentacles" , "Medusa - weak, indecisive person" , "Stinging coelenterate" , "Marine creature with stinging tentacles" , "Marine stinger" .)