Trade mark for a hot iron (5)
I believe the answer is:
brand
I believe this is a double definition.
'trade mark' is the first definition.
(I know that brand is a type of trade mark)
'for a hot iron' is the second definition.
(I've seen this in another clue)
(Other definitions for brand that I've seen before include "Type of product - identifying mark on livestock" , "Comedian" , "Owner's mark on cattle" , "Tradename" , "Type - it's burning" .)