Protuberance, swelling (5)
I believe the answer is:
bulge
I believe this clue is a double definition.
'protuberance' is the first definition.
(synonyms)
'swelling' is the second definition.
(I know that swelling can be written as bulge)
(Other definitions for bulge that I've seen before include "Hump" , "Swelling - sudden increase" , "Protrude" , "Swell" , "Rounded swelling" .)