Develop — cultivate (4)
I believe the answer is:
grow
I believe this is a double definition.
'develop' is the first definition.
(I know that develop can be written as grow)
'cultivate' is the second definition.
(I know that grow is a more specific form of the action cultivate)
(Other definitions for grow that I've seen before include "Swell" , "Develop - propagate" , "Burgeon" , "Become bigger" , "Gain in size" .)