Sci-fi monster's appendage (8)
I believe the answer is:
tentacle
'sci-fi monster's appendage' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tentacle that I've seen before include "Part of octopus" , "Organ used for grasping and feeding" , "Appendage as on octopus" , "Flexible feeling organ" , "Octopus's limb" .)