current transformer in reverse
In principle it would work -- you would get a current in the (original) primary greater than the forced current by a factor equal to the number of secondary turns.

However, the voltage driving this primary loop is very low, and so you would really need low resistance wire in that loop. The resistance of an ammeter would dominate the result and not be representative. If you could use a Hall sensor, or other lossless/low resistance current sensor (another current transformer !), it would work reasonably well.