Transparent cover for her hat? (6)
I believe the answer is:
cloche
This clue is a double definition.
'transparent cover' is the first definition.
(cover for plants)
'her hat?' is the second definition.
(type of woman's hat)
'for' is the link.
(Other definitions for cloche that I've seen before include "Cover put over young plants to protect them from cold" , "It's old hat!" , "Nursery plant protection" , "Style of hat for a woman" , "Horticultural cover" .)