The most common and most likely answer to this crossword clue is the 7 letter word POPOVER
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More clues leading to the result POPOVER
Buddy explains!

The straight part
We know that "muffin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case muffin = popover.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 POPOVER mean?
POPOVER noun- A light hollow muffin, resembling an individual Yorkshire pudding.
- A pop-up element that is rendered over the current web page rather than opening a new tab or window.
- A kind of versatile wraparound dress.