Old garment no good? Smart and hot! (8)
I believe the answer is:
toasting
'hot' is the definition.
(thesaurus)
'old garment no good? smart' is the wordplay.
'old garment' becomes 'toga' (garment worn in ancient Rome).
'no' suggests deleting specific letters.
'good?' becomes 'g' (abbreviation).
'smart' becomes 'sting' (both can mean to burn or hurt).
'toga' with 'g' taken away is 'toa'.
'toa'+'sting'='TOASTING'
'and' is the link.
(Other definitions for toasting that I've seen before include "Raising one's glass" , "Drinking a health to" , "Raising glasses" , "Browning" .)