Associate of two Milan teams heading to training (8)

I believe the answer is:
interact
'associate' is the definition.
The definition and answer can be both to do with social activities as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for interact that I've seen before include "Can't tire (anag)" , "Have a mutual effect" , "Train etc. (anag.)" , "Work with others" , "Show effect on each other" .)
