Fashionable, but not hot (4)
I believe the answer is:
cool
I believe this is a double definition.
'fashionable' is the first definition.
(I've seen this before)
'not hot' is the second definition.
(I know this)
'but' acts as a link.
(Other definitions for cool that I've seen before include "chic" , "Not hot or warm - just unexcited" , "Rain heavily (colloq.)" , "Calm; not warm" , "Lose heat" .)