Swell, widen (7)
I believe the answer is:
distend
I believe this clue is a double definition.
'swell' is the first definition.
(I know that distend is a more specific form of the action swell)
'widen' is the second definition.
(I know that distend is a more specific form of the action the widen)
(Other definitions for distend that I've seen before include "Swell by pressure from within" , "Exaggerate" , "Bloat" , "balloon" , "Make you bulge" .)