Practised poetry with head of department (6)
I believe the answer is:
versed
'practised' is the definition.
(thesaurus)
'poetry with head of department' is the wordplay.
'poetry' becomes 'verse' (lines written in verse).
'with head of' says to take the initial letters.
The first letter of 'department' is 'd'.
'verse'+'d'='VERSED'
(Other definitions for versed that I've seen before include "Is well informed" , "Proficient" , "Well-informed" , "Thoroughly acquainted with and skilled in something" , "Knowing much" .)