Obtain rise (6)
I believe the answer is:
source
'rise' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for source that I've seen before include "Origin; spring" , "Place or person where something begins" , "Origin, starting-point" , "'Origin, root (6)'" , "From which something springs" .)