Insist on having things just right (5)
I believe the answer is:
'insist on' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for exact that I've seen before include "Not approximate; inflict (revenge) on someone" , "Absolutely right" , "Absolutely accurate or correct" , "Spot on, precise" , "Precisely accurate" .)