Mentions old trees (6)
I believe the answer is:
opines
'mentions' is the definition.
The definition and answer 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?
'old trees' is the wordplay.
'old' becomes 'o' (abbreviation).
'trees' becomes 'pines' (pine is a kind of tree).
'o'+'pines'='OPINES'
Can you help me to learn more?
(Other definitions for opines that I've seen before include "'Supposes, considers (6)'" , "Expresses one's view" , "Provides a view" , "Gives a view" , "Offers views" .)