With 16 clues their wordplay leads to a solution where two letters require noted substitutions before entry in the grid. Their definitions have also been swapped around.
16a Set to get excited after moment of boredom (8) Grid entry ...?R?S?E?T
"boredom" is the wrong defn.....i think the correct defn(for the grid entry) is "exclusive"
The wordplay "set to get excited after moment of" gives the answer before 2 letters are changed for the grid entry