Most warm -- and most cool? (7)
I believe the answer is:
hottest
I believe this is a double definition.
'most warm' is the first definition.
('hot' can be a synonym of 'warm')
'most cool?' is the second definition.
(cool and hot can both mean trendy)
'and' is the link.
(Other definitions for hottest that I've seen before include "Most torrid" , "Most heated" , "Most fashionable" , "Of the highest temperature" , "Least cold" .)