The Clue To no ___: in vain
The Answer AVAIL
The phrase "to no avail" means that something was done without success or did not achieve the desired result. In this context, "avail" refers to the effectiveness or usefulness of an action. When we say something was done "to no avail," we are saying it was in vain, as it did not help or change the situation. Therefore, "avail" perfectly fits the crossword clue.