The word wonderwall is a metaphorical term used to describe a person, place, or event.
It is also a compound word.
Wonder- To be filled with admiration, amazement, or
awe.
A curiosity.
Wall- Any of various permanent upright constructions having a length much greater than the thickness and presenting a continuous surface except where pierced by doors,
windows, etc.: used for shelter, protection, or privacy, or to subdivide interior
space, to support floors, roofs, or the like, to retain earth, to fence in an area, etc.
So a wonderwall can be widely considered as a noun that is a strong foundation full of admiration.
In other words, it is
something that gives you strength.
As it is a versatile expression, it
may be used as an adj.