Mac (8)
I believe the answer is:
raincoat
'mac' is the definition.
(macintosh is a type of raincoat)
This is all the clue.
(Other definitions for raincoat that I've seen before include "Catriona (anag.)" , "Wet weather gear" , "protection against the elements" , "Water-resistant outer garment" , "Waterproof outer garment" .)