Date: 202101
Local time of day: 1801-2400
Location: ZZZ.TRACON, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Second aircraft: Small Aircraft; High Wing; 1 Eng; Fixed Gear
Reporter organization: Government
Reporter function: Flight Data / Clearance Delivery; Supervisor / CIC
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Distraction; Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Took Evasive Action
Contributing factors: Environment - Non Weather Related; Human Factors; Staffing
Primary problem: Staffing

Narrative: The RE [RADAR East] was working a busy session and Finals was combined to RW [RADAR West].  However; when Finals is combined; usually the two controllers will each work their own finals traffic.  The RE had Aircraft X on a base leg to Runway XXR at 2;000 feet.  The RW Controller had a VFR Aircraft Y; southbound at 1;800 feet; west of the Runway XXR final approach course.  The RE controller was distracted by another aircraft and forgot to turn Aircraft X.  He went through the final approach course and conflicted with the VFR Aircraft Y.  Both controllers issued traffic and Aircraft Y was able to maintain visual separation from Aircraft X.  However; Aircraft X responded to a TCAS RA and climbed.  Although separation was not lost; the situation was still concerning.I was working the desk and combined with AD [Arrival Data].  I had numerous duties on AD and wasn't able to provide consistent oversight.  However; I observed that it was getting busy on RE and I suggested the controller give his finals traffic to the RW Controller who wasn't as busy.  I did not direct the controller to do so; and so he declined my suggestion.  At the time of the incident; I was coordinating a release off of a satellite airport; as part of my AD duties.I believe that it's getting too busy for the staffing that we currently have.  We only had one Controller on break; so it would have been very difficult to split off another position.  I am consistently having to work AD from the desk; and have been encouraged to do so as much as possible to minimize the number of controllers in the operation during COVID-19.  The need for the CIC to work AD is also because we have so few controllers on the shift.I think I could have been more direct with the Controller; forcing him to hand off his finals traffic instead of suggesting it; and he could have used better techniques; such as not descending the arrival to the same altitude as the VFR aircraft.It should be noted that [personal reason] was the day before this incident.  I'm not sure that that contributed; but I was more tired than normal.




Synopsis: Front Line ATC Manager reported an airborne conflict and cited staffing levels as a contributing factor.