We report on the development of double-cladding active multicore fibre composed of seven single-mode cores of ytterbium doped silica. Laser action in laboratory fibre laser setup is achieved with 61% slope efficiency for optimum fibre length of 14.5 m using incoherent combining of beams generated in each single fibre core. The total mode effective area as a sum of effective areas of generated modes coming out from all cores is 1120 µm², opening perspectives for high power scalability. The measured aggregated beam quality of M² = 17.6 is determined by 95 µm distance between single mode active cores. The proposed fibre is a perspective component for development of high power all-fibre laser for lidars.