Professional study on temperature is supported by model (7)
I believe the answer is:
dentist
'professional' is the definition.
(dentist is a kind of professional)
'study on temperature is supported by model' is the wordplay.
'study' becomes 'den' (den can mean an office or study).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'temperature' becomes 't' (abbreviation).
'supported by' says to put letters next to each other (in a down clue, some letters hold up others).
'model' becomes 'T' (Ford Model T car).
'den'+'t'+'is'+'t'='DENTIST'
(Other definitions for dentist that I've seen before include "Tooth surgeon" , "Treatment provider for teeth" , "Teeth specialist" , "Occasional driller" , "One who treats teeth" .)