Sort

SORT was published in the August 2019 issue of Crossword 496, the preamble goes:

Six symmetrically placed across solutions, whose unchecked letters could provide the title, should be read together to indicate how solvers must replace them.  Every clue generates an extra letter in wordplay not used by the solution.  In clue order these extra letters spell out a further instruction.

Solution Grids

Final Grid

Initial Grid

Solvers were required to select six symmetrically placed across entries (with SORT as their only unchecked letters) which provided a coherent instruction.  These were USER, OMAN, NUMB, ERIN, GINS and TEAD.  When concatenated, these provide the instruction, “USE ROMAN NUMBERING INSTEAD”.  Each of the six entries should be replaced by the four letter equivalent of their clue number.  Extra letters in wordplay spell HIGHLIGHT SUM OF REPLACED ENTRIES FOUND IN STRAIGHT LINE.  The sum of the six new entries is 17+22+24+26+29+35 = 153, which can be found (also in roman numerals) in a straight line in the NW corner of the grid (CLIII).