The sauce in this barrel is hot stuff! (6)
I believe the answer is:
relish
'the sauce' is the definition.
(I've seen this before)
'this barrel is hot stuff' is the wordplay.
'stuff' indicates the answer is hidden within the clue (I've seen 'stuffing' mean this).
'RELISH' can be found hidden inside 'this barrel is hot'.
'in' is the link.
(Other definitions for relish that I've seen before include "Enthusiastic enjoyment of a condiment" , "Savour and enjoy food." , "Greatly enjoy; pickle" , "Enjoy greatly - such sauce!" , "appetizer?" .)