The most common and most likely answer to this crossword clue is the 9 letter word VAGABONDS
I've seen this crossword clue in The Times
V
A
G
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Buddy explains!

The straight part
We know that "tramps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tramps = vagabonds.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 VAGABONDS mean?
VAGABONDS noun- A person on a trip of indeterminate destination and/or length of time.
- One who wanders from place to place, having no fixed dwelling, or not abiding in it, and usually without the means of honest livelihood; a vagrant; a hobo.