Crossword Genius

A picture one will carry everywhere (6)

Ross

I believe the answer is:

tattoo

I'm a little stuck... Click here to teach me more about this clue!

'a picture' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for tattoo that I've seen before include "Military call and design on the skin" , "Edinburgh military parade" , "Military display - skin design" , "Indelible picture or design on skin" , "Pointedly design" .)

I've seen this clue in The Globe and Mail.
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