Increased, ballooned (4)
I believe the answer is:
grew
I believe this clue is a double definition.
'increased' is the first definition.
(growing is a kind of increasing)
'ballooned' is the second definition.
(I've seen this in another clue)
(Other definitions for grew that I've seen before include "Cultivated'" , "Sprouted" , "Expanded - flourished" , "Became larger" , "Multiplied" .)