Natural, like an empty gallery? (7)

I believe the answer is:

artless

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

'natural' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

(Other definitions for artless that I've seen before include "Simple, unaffected" , "Naive - unskilful" , "as an empty gallery" , "Without guile or affectation" , "Without guile or sophistry" .)

I've seen this clue in the Sydney Morning Herald.

Want a hint initially instead of a full solution? Install my app