If you can’t find any themes or common elements in the grid, there’s always another place to look. . .
. . . the clues.
Do any of them seem convoluted when much simpler ways of cluing the entry are at hand?
Some of the clues have an element in common.
That element has nothing to do with the words or letters in the clues.
It’s an element of crossword cluing.
There are ten of them.
The initial letters of the entries for those clues spell out the answer.
For 25A, the answer is literal; for 18A, it’s more metaphorical.