The most common and most likely answer to this crossword clue is the 10 letter word AGGREGATOR
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The straight part
We know that "one who/collects things" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one who/collects things = aggregator.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 AGGREGATOR mean?
AGGREGATOR noun- Someone or something which aggregates
- An online feed reader used to keep track of updates to blogs, etc.