Be closely involved in short treatise about English (8)
I believe the answer is:
interact
'be closely involved' is the definition.
I can't tell whether this defines the answer.
'in short treatise about english' is the wordplay.
'short treatise' becomes 'tract' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'english' becomes 'E' (abbreviation).
'tract' going around 'e' is 'teract'.
'in'+'teract'='INTERACT'
Can you help me to learn more?
(Other definitions for interact that I've seen before include "Train etc. (anag.)" , "Have a mutual effect" , "Work closely together" , "Mix with each other" , "Affect one another mutually" .)