Less fair and more sinister (6)

I believe the answer is:

darker

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

'more sinister' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

(Other definitions for darker that I've seen before include "Less illuminated" , "More deficient in light" , "More gloomy" , "Dimmer, murkier" .)

I've seen this clue in The Irish Independent.

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