Prosper, flourish (6)
I believe the answer is:
thrive
This clue is a double definition.
'prosper' is the first definition.
(I know that prosper can be written as thrive)
'flourish' is the second definition.
(I know that flourish can be written as thrive)
(Other definitions for thrive that I've seen before include "Do well, flourish" , "Grow vigorously, flourish" , "Prosper, grow well" , "Grow strongly" , "Prosper, flourish" .)