Architect’s means of keeping the rain out (10)
I believe the answer is:
mackintosh
'architect's' is the definition.
(architect Charles Rennie Mackintosh)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for mackintosh that I've seen before include "Architect" , "Raincoat" , "providing protection from the elements" , "waterproof layer" , "Garment" .)