The most common and most likely answer to this crossword clue is the 7 letter word SQUIDGE
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Buddy explains!

The straight part
We know that "mash?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mash? = squidge.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 SQUIDGE mean?
SQUIDGE noun- A tight space; squeeze.
- (tiddlywinks) The act of firing a wink with a squidger.
- To squash, most often between one's fingers.
- (tiddlywinks) To fire a wink with a squidger.