Spooner says brown hair is boring (7)

I believe the answer is:

mundane

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

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

I cannot understand how the rest of the clue works.

(Other definitions for mundane that I've seen before include "Everyday, humdrum" , "Ordinary, of this world" , "Lacking excitement; worldly" , "Boring" , "Banal; earthly" .)

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

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