Increase Aunt Meg's confusion (7)
I believe the answer is:
augment
'increase' is the definition.
(I know that augment is a more specific form of the action grow)
'aunt meg's confusion' is the wordplay.
'confusion' indicates anagramming the letters.
'aunt'+'meg'='auntmeg'
'auntmeg' anagrammed gives 'AUGMENT'.
(Other definitions for augment that I've seen before include "Swell" , "Expand" , "get longer" , "Enlarge or increase" , "Increase number of" .)