The most common and most likely answer to this crossword clue is the 7 letter word ABATING
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The straight part
We know that "letting up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case letting up = abating.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ABATING mean?
ABATING verb- (obsolete outside law) To put an end to; to cause to cease.
- To become null and void.
- To nullify; make void.
- To humble; to lower in status; to bring someone down physically or mentally.
- To be humbled; to be brought down physically or mentally.
- To curtail; to deprive.
- To reduce in amount, size, or value.
- To decrease in size, value, or amount.
- To moderate; to lessen in force, intensity, to subside.
- To decrease in intensity or force; to subside.
- To deduct or omit.
- To bar or except.
- To cut away or hammer down, in such a way as to leave a figure in relief, as a sculpture, or in metalwork.
- To dull the edge or point of; to blunt.
- To destroy, or level to the ground.
- To enter a tenement without permission after the owner has died and before the heir takes possession.
- Anesis.