Appearance affects space and time (6)
I believe the answer is:
aspect
'appearance' is the definition.
(I know that aspect is a type of countenance)
'affects space and time' is the wordplay.
'affects' indicates anagramming the letters (I've seen 'affecting' mean this).
'and' is a charade indicator (letters next to each other).
'time' becomes 't' (abbreviation).
'space' is an anagram of 'aspec'.
'aspec'+'t'='ASPECT'
(Other definitions for aspect that I've seen before include "'Appearance, facet (6)'" , "'Appearance, outlook (6)'" , "Face" , "Distant view of a wide area" , "Scene, panorama" .)