a last-ditch attempt to solve a problem is the final attempt that you make after you have failed several times to solve it.

The gesture has been seen by many as a last-ditch attempt to win voters. (always before noun)

The UN is trying to secure talks between the two sides in a last-ditch effort to avert war.

• not hold water
• not hold your breath
• not hold your liquor
• not hurt a fly
• not if can help it
• not if you can help it
• not in a month of Sundays
• not in my wildest dreams
• not in the business of
• not in the business of doing something
• not in the least
• not in the same league
• not in the slightest
• not judge a book by its cover
• not know beans about
• not know beans about something
• not know from Adam
• not know if are coming or going
• not know if you are coming or going
• not know someone from Adam
• not know the first thing about
• not know the first thing about something
• not know the half of it
• not know the meaning of the word
• not know what hit