Man who may impose a rigid measure? (5)
I believe the answer is:
ruler
This clue might be a double definition.
'man who may impose' 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?
'a rigid measure?' is the second definition.
(rigid tool for measuring things)
Can you help me to learn more?
(Other definitions for ruler that I've seen before include "Thoroughly straight" , "Drawing stick or monarch" , "Source of line" , "Straight edge; monarch" , "Queen maybe" .)