Instruct or admonish (7)
I believe the answer is:
lecture
This clue is a double definition.
'instruct' is the first definition.
(I know that lecture is a type of instruct)
'admonish' is the second definition.
(thesaurus)
'or' is the link.
(Other definitions for lecture that I've seen before include "Instructive discourse" , "Teaching discourse" , "Deliver a talk" , "Formal talk on a subject" , "An instructive talk, in school or church" .)