The most common and most likely answer to this crossword clue is the 7 letter word DUSTMAN
I've seen this crossword clue in The Daily Telegraph
D
U
S
T
M
A
N
Buddy explains!

The straight part
We know that "collector" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case collector = dustman.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 DUSTMAN mean?
DUSTMAN noun- A person employed to collect refuse from people's homes and take it to be processed.