Be friendly and prosper (3,2)
I believe the answer is:
get on
'prosper' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for get on that I've seen before include "Age; prosper" , "What boarders do" , "Make progress or climb aboard" , "Make progress or mount up" , "Hit it off" .)