/usr/share/metview/etc/MXSectionDef is in metview-data 4.8.0-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | MXSECTION; Metview 4; Specific Application
{
    DATA
        [
            interface       = icon,
            class           = GRIB,
            exclusive       = false,
            help            = help_data,
            help_directory  = '/System/Defaults',
            help_name       = Data for XSection,
            help_class      = RETRIEVE,
            help_definition = ( RETRIEVE, TYPE = FC, LEVTYPE = PL,
                                PARAM = T, DATE = '-1',
                                LEVELIST = 1000/850/700/500/400/300,
                                STEP = 12, GRID = 1.5/1.5 ) 
        ]
    { @ }
   %include MXSectionCommonDef
   BOTTOM_LEVEL
   {
      *
   } = 1100.0
   TOP_LEVEL
   {
      *
   } = 0.01
}
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