Steamy and hot on the outside, turning purple (8)
I believe the answer is:
amethyst
'purple' is the definition.
(thesaurus)
'steamy and hot on the outside turning' is the wordplay.
'and' says to put letters next to each other (I've seen this in other clues).
'on the outside' means to remove the middle letters.
'turning' indicates anagramming the letters.
'hot' with its centre removed is 'ht'.
'steamy' put after 'ht' is 'htsteamy'.
'htsteamy' anagrammed gives 'AMETHYST'.
(Other definitions for amethyst that I've seen before include "Variety of quartz" , "Semiprecious stone of violet or purple quartz" , "Transparent bluish quartz" , "A Middle East language" , "Purple quartz, used as a gemstone" .)