Machine that could ruin pork pie merchant? (3,8)
I believe the answer is:
lie detector
'machine that could ruin' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'pork pie merchant?' is the wordplay.
'pork pie' becomes 'lie' (I've seen this before).
'merchant?' becomes 'detector' (I can't explain this - if you can you should give a lot more credence to this answer).
'lie'+'detector'='LIE-DETECTOR'
Can you help me to learn more?
(Other definitions for lie detector that I've seen before include "Forensic equipment" , "Machine for establishing truth" , "Truth-determining device" , "help to tell a story" , "It may check someone's veracity" .)