Fashionable chap is cold (9)
I believe the answer is:
inclement
'is cold' is the definition.
(thesaurus)
'fashionable chap' is the wordplay.
'fashionable' becomes 'in' (in can mean fashionable or trendy).
'chap' becomes 'clement' ().
'in'+'clement'='INCLEMENT'
(Other definitions for inclement that I've seen before include "Weather so awful" , "severe" , "not fair" , "bitter" , "(Of weather) bad" .)