Eight across solutions are one letter too long for their allotted space; these letters should be dropped to produce another word for entry in the grid. Eight down solutions are one letter too short and one of the above eight letters must added to produce a word for entry in the grid. The eight letters involved make an anagram for an appropriate word. Each of the remaining 16 clues contains a superfluous word (or words), which provide definitions for the 16 new solutions in the grid.
I think that one ended up as Steal. Seal,confirmation, hidden in the clue and add a T from an Across answer. (This crossword is a couple of weeks old, I no longer have my copy.)