The most common and most likely answer to this crossword clue is the 5 letter word ALLAY
A
L
L
A
Y
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The straight part
We know that "Lull" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lull = allay.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 ALLAY mean?
ALLAY noun- Alleviation; abatement; check.
- An alloy.
- To make quiet or put at rest; to pacify or appease; to quell; to calm.
- To alleviate; to abate; to mitigate.
- To subside, abate, become peaceful.
- To mix (metals); to mix with a baser metal; to alloy; to deteriorate.
- (by extension) To make worse by the introduction of inferior elements.