Do some arithmetic and make sense (3,2)
I believe the answer is:
add up
'make sense' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for add up that I've seen before include "Aggregate, get total" , "Reckon" , "Ring true" , "Seem consistent or reasonable - arithmetically?" , "Point to a reasonable conclusion" .)