Citation X (C750)
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Confusion; Communication Breakdown
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Returned To Clearance
Human Factors; Procedure
After departing Runway XXR at ZZZ crew was eventually vectored for arrival Runway XX at ZZZ1.  Crew was in visual conditions and planned to use ILS Z Runway XX guidance as back up for visual condition arrival.  Crew advised ZZZ1 in sight west of ZZZ heading easterly.  Aircraft was at 3;300 ft. MSL and ZZZ Approach cleared Aircraft to cross ZZZ at 3;000 ft. cleared for the visual Runway XX.  Crew was at the western boundary of ZZZ but had the approach mode preselected and just over the top of ZZZ is captured the GS and we began to descend following the glide path. We descended about 150 ft. and continued for landing.  Crew landed ZZZ1 without incident.  Crew has elected to file and ASRS report due to possible difference in the understanding of cross over meaning.  If the Controller wanted us at 3;000 ft. the entire time we crossed ZZZ then this event could be taken as an altitude deviation.  If that statement only meant to start at 3;000 ft. then there is none. If flying the published ILS Z approach; it is stated to be at 3;000 ft. until glide slope intercept. 1. Task saturation with such a short flight.  While we were not rushing to complete the flight; and had measures in place to mitigate as much as possible; there are always opportunities for saturation. 2. Instructions that I perceive lend themselves to interpretation or possible confusion after thinking about the events.  3. At the time the crew nor ATC received/gave further clarification. 4.  As PM (Pilot Monitoring) I should have been more aware of the FGC selections that had been set and had stronger SA (Situational Awareness) to determine how it might affect our path. 5. Crew's technique for using FGC/Automation instead of splitting flight path and vertical guidance using FGC and AP vs combining them using the APP mode. To ensure complete and unquestioned compliance with this instruction again; crew should ensure that altitude is held till absolutely clear of airport boundary and then aviate appropriately to return aircraft flight path and vertical progress to desired slope.
[Report Narrative Contained No Additional Information.]
Flight crew reported altitude deviation on confusing clearance.