I think it's been years since I saw ChingDong-Ya last.
According to the dictionary, ChingDong-Ya's defenition is
Japanese group of traditional street performers with bright-colored clothes and makeup
or a band of musical sandwichmen.
I hope this explanation is good enough to understand.
Ching is the sound of bells and Dong is of drums.
"Ya" is a convenient word we can add to most kind of vendors and shops.
A CD shop is called CD-ya for example.

When I was little I often see ChingDong-Ya people marching down
the neighborhood playing various kinds of musical instruments,
wearing big advertisement boards on their backs.

These days we seldom see ChingDong-Ya anymore.
I have once seen a documentary program on TV
reporting that they don't have young successors for this job.

When I was a teenager girl,
my mother would often tell me that I looked like a ChingDong-Ya,
which means she didn't like the bold design clothes I liked to wear.
"You look like a ChingDong-Ya(so you wil be laughed at)"
was very common term for mothers to tell their daughters back then,
but now I don't know if young people of today can
understand its meaning.
Time has been changed.