One present at a number of Dragnet's regular shows (9)
I believe the answer is:
attendant
'one present' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for attendant that I've seen before include "Assistant" , "Related" , "Servant; accompanying" , "escort" , "Person present as companion or servant" .)