|We present a relationship between the dynamics of ∼3-min slow magnetoacoustic waves in the sunspot and flare emergence process. Waves propagating in the magnetic channel, whose one foot is anchored in the umbra, represent the disturbing agent responsible for triggering the flare energy release. We applied time-distance plots and pixels wavelet filtration technique (PWF-analysis) to obtain spatio-temporal distribution of wave power variations in radio and SDO/AIA data. In the correlation curves of the 17 GHz (NoRH) radio emission, we found a monotonous energy amplification of the 3-min waves in the sunspot umbra before the 2012 June 7 flare. This amplification was associated with an increase in the length of the oscillatory wakes in coronal loops (SDO/AIA, 171 Å) prior to the flare onset. A peculiarity of the flare is the flat site of the flare emission in soft X-rays (RHESSI, 3–25 keV) after the short impulsive phase, which indicates continuing energy release. Throughout this time, we found transverse oscillations of the flare loop with a 30 s period in the radio-frequency range (NoRH, 17 GHz). This period appears to be related to the 3-min waves from the sunspot. The magnetic field extrapolation based on SDO/HMI magnetograms shows the existence of the magnetic channel (waveguide) connecting the sunspot with the energy release region. We suppose that MHD-waves propagating from sunspots be able to transform into transversal high-frequency oscillations, and to initiate a forced reconnection in magnetic structures.