Threat come wildly, with which to gauge revolutions (10)
I believe the answer is:
tachometer
'threat come wildly with which to gauge revolutions' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'threat come wildly' is the wordplay.
'wildly' indicates anagramming the letters.
'threat'+'come'='threatcome'
'threatcome' with letters rearranged gives 'TACHOMETER'.
Can you help me to learn more?
(Other definitions for tachometer that I've seen before include "It measures revolutions" , "Instrument measuring speed of rotation" , "Teacher Tom (anag.)" , "rev counter" .)