Ruler to ascend (5)
I believe the answer is:
scale
This could be a double definition.
'ruler' is the first definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'ascend' is the second definition.
(thesaurus)
'to' acts as a link.
Can you help me to learn more?
(Other definitions for scale that I've seen before include "Climb; overlapping plate" , "Tones rising maybe" , "See 23" , "Doh, re, me etc" , "Climb, or series of notes in music" .)