At first I thought...of course..but with a side fan...doubt it but can't confirm that. However, since the side fan is in the lower position it should work. Most cases work if side fan is lower than CPU cooler.
In case anyone stumbles on this, the answer is "yes". My ARC Midi R2 (which is nearly identical to the Define R4--to the point that the side panels are interchangeable between the two) is running a Noctua NH-D15S (a *big* CPU cooler; same height as the D14, and 10mm wider) with a Noctua NF-P14FLX on the side panel.