  We present multispectral analysis (radio, H$\alpha$, UV/EUV, and hard X-ray)
of a confined flare from 2015 March 12. This flare started within the active
region NOAA 12 297 and then it expanded into a large preexisting magnetic rope
embedded with a cold filament. The expansion started with several brightenings
located along the rope. This process was accompanied by a group of slowly
positively drifting bursts in the 0.8--2 GHz range. The frequency drift of
these bursts was 45 -- 100 MHz s$^{-1}$. One of the bursts had an S-like form.
During the brightening of the rope we observed an unique bright EUV structure
transverse to the rope axis. The structure was observed in a broad range of
temperatures and it moved along the rope with the velocity of about 240 km
s$^{-1}$. When the structure dissipated, we saw a plasma further following
twisted threads in the rope. The observed slowly positively drifting bursts
were interpreted considering particle beams and we show that one with the
S-like form could be explained by the beam propagating through the helical
structure of the magnetic rope. The bright structure transverse to the rope
axis was interpreted considering line-of-sight effects and the
dissipation-spreading process, which we found to be more likely.
