Cigars forming hot cores (8)
I believe the answer is:
cheroots
'cigars' is the definition.
(cheroot is a kind of cigar)
'forming hot cores' is the wordplay.
'forming' indicates an anagram.
'hot'+'cores'='hotcores'
'hotcores' with letters rearranged gives 'CHEROOTS'.
(Other definitions for cheroots that I've seen before include "small cigars" , "Cigars with both ends cut flat" , "Cigars with both ends open" , "Square-ended cigars" , "Cigars with both ends cut square" .)