Achieve mounting progress? (3,2)
I believe the answer is:
get on
'progress?' is the definition.
('get on' can be a synonym of 'progress')
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for get on that I've seen before include "Make progress; be friends" , "Make progress or mount up" , "Board - prosper" , "Board; establish good relations" , "Age; prosper" .)