Often we might fly something like 160 kts to 4 miles, so by saying reduce to minimum approach speed they are just saying come back to V approach. Many airports have the 160 to 4, so they might say this to you at 5 miles for example.
Another phrase used is 'reduce to minimum clean.' This would just mean the minimum maneuvering speed with no slat or flap. In the A32x and others this would be green dot speed, this is displayed as a green dot on our speed tape. This 'characteristic' speed varies with weight and altitude.
We wouldn't intentionally fly below the normal V approach.
Cheers.