TRACON Controller reported a traffic conflict due to a UAS that descended below its assigned altitude near a crewed aircraft that was on departure.

Narrative

Aircraft X was on departure from VCV initially climbing to 070. I first cleared them ZZZ [VORTAC]...ZZZ1 [VORTAC] flight plan route and to climb to 130. Very quickly I realized that the climb could potentially be a conflict with UAV maneuvering VFR at 090. I amended Aircraft X clearance to direct ZZZ1 [VORTAC] and to climb to 080. I continued my scan around the scope and when I went back I noticed that UAV was descending into Aircraft X; it was at this time I capped the UAV at or above 085 and called traffic on the Aircraft X climbing to 080. I then also called the traffic for Aircraft X on the UAV and that they were capped at or above 085. I scanned around again and Aircraft X called the UAV in sight. When I went back to the aircraft I noticed that UAV had continued his descent further into Aircraft X. Due to the proximity of the aircraft I was not able to safely offer alternate instructions to either aircraft.UAV aircraft are constantly maneuvering west of VCV at various altitude and controllers need to cap departures in order to avoid them. There should be a dedicated area away from NAS traffic [so] the UAV can maneuver safely away from others.