Frank possibly callous in EastEnders (7)

I believe the answer is:

artless

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

'frank' is the definition.
(artless can mean frank or candid)

I don't understand the rest of the clue.

(Other definitions for artless that I've seen before include "Clumsy and uncaring" , "Plain" , "Simple, unaffected" , "as an empty gallery" , "Natural - uncontrived" .)

I've seen this clue in The Telegraph.

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