Is it measured in round figures? (13)
I believe the answer is:
circumference
'round figures?' is the definition.
'circumference' can be an answer for 'round' (thesaurus). I'm unsure of the 'figures?' bit.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for circumference that I've seen before include "Earth's is circa twenty-five thousand miles" , "Perimeter of circle" , "Distance around circle" , "Exterior of circle" , "Boundary of a circle" .)