VMS Help TCPIP Services, TELNET, TN3270 Keyboard Functions, ER_EOF  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    VT100: EXT + KP,            VT200: F18
    DEFINE_KEY Function: ERASE_EOF

    Erases the contents of the current field, from the location of
    the cursor to the end of the field. The cursor remains in the
    same location.