Preach or otherwise chastise (8)
I believe the answer is:
reproach
'chastise' is the definition.
The answer and definition can be both to do with communicating as well as being verbs in their base form.
Maybe there's an association between them I don't understand?
'preach or otherwise' is the wordplay.
'otherwise' indicates anagramming the letters.
'preach'+'or'='preachor'
'preachor' is an anagram of 'REPROACH'.
Can you help me to learn more?
(Other definitions for reproach that I've seen before include "Castigate" , "Express disapproval, admonish" , "Berate" , "approval? Just the opposite" , "Express disapproval to (someone)" .)