Started dietitian off (9)
I believe the answer is:
initiated
'started' is the definition.
(initiating is a kind of starting)
'dietitian off' is the wordplay.
'off' is an anagram indicator.
'dietitian' is an anagram of 'INITIATED'.
(Other definitions for initiated that I've seen before include "Begun" , "Started" , "Began" , "Accepted into a group by way of a ritual" , "Those admitted into the mysteries" .)