The most common and most likely answer to this crossword clue is the 5 letter word HUGER
H
U
G
E
R
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The straight part
We know that "more fat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case more fat = huger.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 HUGER mean?
HUGER adjective- Very large.
- Distinctly interesting, significant, important, likeable, well regarded.