Female artist round back of Tate, one regulating courses (9)
I believe the answer is:
dietitian
'one regulating courses' is the definition.
(someone managing a diet ie courses of food)
'female artist round back of tate' is the wordplay.
'female' becomes 'di' (short for Diana).
'artist' becomes 'titian' (16th-century painter).
'round' means one lot of letters goes inside another.
'back of' suggests the final letters.
The final letter of 'tate' is 'e'.
'di'+'titian'='dititian'
'dititian' enclosing 'e' is 'DIETITIAN'.
(Other definitions for dietitian that I've seen before include "one who regulates courses" , "Initiated for food expert" , "Medical adviser" , "Food guru" , "Food specialist" .)