usta- vb. "burn" (transitive) (LT1:271, QL:98). This form reflects the stem USU listed in early material; however, since Tolkien seems to have changed it to UR later, we should perhaps read *urta- for usta-.
Quenya
urta-
verb. urta-
usta-
burn
urta-
verb. to burn
*urta-, see usta-