The most common and most likely answer to this crossword clue is the 10 letter word COLLECTING
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Buddy explains!

The straight part
We know that "hoarding" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hoarding = collecting.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 COLLECTING mean?
COLLECTING verb- To gather together; amass.
- To get; particularly, get from someone.
- To accumulate (a number of similar or related objects), particularly for a hobby or recreation.
- To form a conclusion; to deduce, infer. (Compare gather, get.)
- (often with on or against) To collect payments.
- To come together in a group or mass.
- To infer; to conclude.
- (of a vehicle or driver) To collide with or crash into (another vehicle or obstacle).
- A hobby including seeking, locating, acquiring, organizing, cataloging, displaying, storing, and maintaining whatever items are of interest to the individual collector.