For some terminals clear erases only the portion of the plotting surface defined by set size, so for these it can be used in conjunction with set multiplot to create an inset.
Example:
set multiplot plot sin(x) set origin 0.5,0.5 set size 0.4,0.4 clear plot cos(x) unset multiplot
Please see set multiplot (p. ), set size (p. ), and set origin (p. ) for details.