To outline the design and rationale of clock, a large, phase III randomized controlled trial which examines the role vascular clamping during robot-assisted partial nephrectomy (RAPN) for localized renal cancer. To be eligible for study entry, patients must have normal coagulative function, preoperative estimated glomerular filtration rate (eGFR) >60 mL/min, normal contralateral kidney and a single renal mass with RENAL Score ≤10. Eligible patients are to be randomized in a 1:1 ratio between two arms. Randomized allocation was assigned by a permuted block design, stratified by center. Allocation arm was notified by the study internet-based e-form, managed by an independent software house. Arm A=RAPN with ischemia; Arm B=RAPN without ischemia. At any moment, from randomization to the end of the procedure, the investigators could amend the indication given by randomization and shift to the alternative clamping option, detailing the timing and reasons of their decision. CLOCK is a randomized controlled trial, which addresses two questions relating to the management of localized renal cancer treated by RAPN with or without ischemia: 1) what is the impact of the surgical technique on long-term renal function; 2) what are the factors influencing the shift from one technique to the other. The study will be completed 24 months after the last enrollment.