Party he arranged after reading treatment (6,7)
I believe the answer is:
speech therapy
'treatment' is the definition.
(I know that speech therapy is a type of therapy)
'party he arranged after reading' is the wordplay.
'arranged' indicates an anagram (letters rearranged).
'after' says to put letters next to each other.
'reading' becomes 'speech' (I can't justify this - if you can you should believe this answer much more).
'party'+'he'='partyhe'
'partyhe' is an anagram of 'therapy'.
'therapy' put after 'speech' is 'SPEECH THERAPY'.
Can you help me to learn more?
(Other definitions for speech therapy that I've seen before include "Diction treatment" , "Treatment to facilitate talking" , "Treatment of communication disorders" .)