A sonic lance was a sonic device used primarily for cutting.
The sonic screwdriver had a sonic lance as one of its removable heads. The Fourth Doctor used it to cut out a lock. (DW: Robot)
A small version once carried by the Sixth Doctor may have had chiefly medical applications, though this gave it secondary utility as a short-range weapon. Like the Doctor's sonic screwdriver, however, it had a variety of uses beyond the function its name conveyed. Thus, while it was seen to allow the Doctor to cut wires whilst repairing his TARDIS, it also helped the Cryon, Flast, to heat up an explosive compound. (DW: Attack of the Cybermen).
Sonic lances were also available commercially in some places. A larger version — in no way associated with the Doctor — was used on the planet Peladon for the purpose of mining. Ettis tried to use this lance in his rebellion; having it taken to Mount Megeshra from where to attack the citadel. (DW: The Monster of Peladon)
Sonic lances were carried by the Arucha. (WC: The War of Art)