Outer aspect of a building with an advert in front (6)
I believe the answer is:
facade
'outer aspect of a building with' is the definition.
I can't tell whether this definition defines the answer.
'advert in front' is the wordplay.
'advert' becomes 'ad' (synonyms).
'in' is an insertion indicator.
'front' becomes 'face' (synonyms).
'ad' going within 'face' is 'FACADE'.
'an' acts as a link.
Can you help me to learn more?
(Other definitions for facade that I've seen before include "Front; work by Walton" , "Front - mask" , "Show" , "False front" , "Frontage or veneer" .)