Small Aircraft; High Wing; 1 Eng; Fixed Gear
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 0; Flight Crew Total 23000; Flight Crew Type 500
Communication Breakdown; Distraction; Training / Qualification; Confusion
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance
Procedure; Chart Or Publication; Environment - Non Weather Related; Human Factors
I had not flown since March of this year; due to all the COVID virus going on nationwide. A friend asked me to reposition a newly acquired aircraft from ZZZ1 to ZZZ2. Weather was currently and forecast to be VFR the entire route; but I filed it IFR to get myself back to speed on instruments; which I thought I did a good job of this trip. My first stop was ZZZ for fuel. Had gotten dark by then; about XA:30pm local time. [My] clearance departing was to fly the 'ZZZZZ X to ZZZZZ [Intersection]; then on course'...as I heard it and understood. My next intersection; which I had filed to from the airport was ZZZZZ1 Intersection. So that is where I was attempting to navigate to after I passed ZZZZZ. So ATC calls me on radio and says I was supposed to fly on to ZZZZZ2 Intersection and then do the 15 mile arc around to ZZZZZ1. (This was not what I understood in the departure clearance.) They vectored me on towards ZZZZZ1; and I continued.I should have asked for vectors before departing the airport; instead of the SID. The GPS in the airplane was not quick/easy to alter any data; but I was doing OK with it enroute.
GA pilot reported a track deviation during departure and cited clearance confusion as a contributing factor.