Trio elected new truth gauge (3,8)
I believe the answer is:
lie detector
'truth gauge' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'trio elected new' is the wordplay.
'new' indicates anagramming the letters.
'trio'+'elected'='trioelected'
'trioelected' anagrammed gives 'LIE-DETECTOR'.
Can you help me to learn more?
(Other definitions for lie detector that I've seen before include "Truth-finding machine" , "Machine for establishing truth" , "Editor elect (anag.)" , "Police polygraph" , "Truth-determining device" .)