Space in ever-changing facade (6)
I believe the answer is:
veneer
'facade' is the definition.
(I've seen this before)
'space in ever-changing' is the wordplay.
'space' becomes 'en' (in printing, a space as wide as a letter 'n').
'in' indicates putting letters inside.
'changing' indicates an anagram.
'ever' anagrammed gives 'veer'.
'en' inserted inside 'veer' is 'VENEER'.
(Other definitions for veneer that I've seen before include "Decorative surface layer" , "Thin covering on top, as of wood" , "Disguise" , "Thin covering on the outside" , "Thin wooden facing" .)