Celebrity confined to earth, hot stuff (7)
I believe the answer is:
mustard
'hot stuff' is the definition.
'celebrity confined to earth' is the wordplay.
'celebrity' becomes 'star' (I've seen this before).
'confined to' means one lot of letters goes inside another.
'earth' becomes 'mud' (mud is a kind of earth).
'star' going inside 'mud' is 'MUSTARD'.
(Other definitions for mustard that I've seen before include "Yellow sauce" , "Type of Brassica" , "Murderer" , "Pungent powder or paste" , "Powdered seeds used to make condiment" .)