Shapeless mass; swelling (4)
I believe the answer is:
lump
I believe this clue is a double definition.
'shapeless mass' is the first definition.
(I've seen this before)
'swelling' is the second definition.
(I know that swelling can be written as lump)
(Other definitions for lump that I've seen before include "Large piece without definite shape" , "Node" , "Gross" , "Chunk, clod, nodule" , "Small solid mass" .)