Shapeless mass (4)
I believe the answer is:
blob
'shapeless mass' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for blob that I've seen before include "Something small, soft and round" , "Drop of thick liquid or viscous substance" , "Mark signifying nothing" , "Globule; round spot" , "Indistinct shape" .)