Quantity of current beginning to matter in motionless crushing machine (5,4)
I believe the answer is:
stamp mill
'motionless crushing machine' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'quantity of current beginning to matter in' is the wordplay.
'quantity of' becomes 'still' (I can't explain this - if you can you should believe this answer much more).
'current' becomes 'amp' (electricity).
'beginning to' suggests taking the first letters.
'in' means one lot of letters goes inside another.
The first letter of 'matter' is 'm'.
'amp'+'m'='ampm'
'still' enclosing 'ampm' is 'STAMP-MILL'.
Can you help me to learn more?
(Another definition for stamp mill that I've seen is " machine designed to crush".)