Unhealthy paleness (6)
I believe the answer is:
pallor
'unhealthy paleness' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for pallor that I've seen before include "showing whiteness" , "Lack of facial colour as from illness" , "Ashen complexion due to illness" , "Paleness of complexion" , "Colourlessness" .)