Hot or warm (7)
I believe the answer is:
thermal
I believe this clue is a double definition.
'hot' is the first definition.
(similar in meaning)
'warm' is the second definition.
(similar in meaning)
(Other definitions for thermal that I've seen before include "Pertaining to heat" , "Upward current of warm air" , "Up-current of air" , "Related to heat" , "type of baths" .)