The most common and most likely answer to this crossword clue is the 8 letter word RANSACKS
I've seen this crossword clue in Financial Times
R
A
N
S
A
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Buddy explains!

The straight part
We know that "rifles through" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rifles through = ransacks.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 RANSACKS mean?
RANSACKS verb- To loot or pillage. See also sack.
- To make a vigorous and thorough search of (a place, person) with a view to stealing something, especially when leaving behind a state of disarray.
- To examine carefully; to investigate.
- To violate; to ravish; to deflower.