Promotes distributing sedatives across river (10)
I believe the answer is:
advertises
'promotes' is the definition.
The answer and definition can be both to do with communicating as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?
'distributing sedatives across river' is the wordplay.
'distributing' indicates an anagram.
'across' is an insertion indicator.
'river' becomes 'r' (abbreviation).
'sedatives' anagrammed gives 'advetises'.
'advetises' placed around 'r' is 'ADVERTISES'.
Can you help me to learn more?
(Other definitions for advertises that I've seen before include "Plugs (colloq.)" , "Steve raids (anag.)" , "Publicises" , "Pushes" .)