He is known by his acts (10)
I believe the answer is:
legislator
'his acts' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he is known by' is the wordplay.
I cannot quite see how this works, but
'is' is found in the answer.
'by' could be 'at' and 'at' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for legislator that I've seen before include "One in Westminster perhaps" , "lawman" , "Lawmaker" , "Parliamentarian" , "Lawgiver" .)