Wide-brimmed Mexican hat (8)
I believe the answer is:
sombrero
'wide-brimmed mexican hat' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sombrero that I've seen before include "a Mexican's overheads" , "Straw hat with very wide brim from Mexico" , "Large Mexican sun-hat" , "Wide-brimmed hat of Mexico" , "Hat for South American" .)