Communicated with head of French department, initially, around ten (6)
I believe the answer is:
texted
'communicated with head of' is the definition.
The definition suggests a past participle verb which matches the answer.
'french department initially around ten' is the wordplay.
'french' becomes 'tete' (I am not sure about this - if you are sure you should believe this answer much more).
'initially' indicates taking the first letters.
'around' is an insertion indicator.
'ten' becomes 'X' (Roman numeral).
The first letter of 'department' is 'd'.
'tete'+'d'='teted'
'teted' going around 'x' is 'TEXTED'.
Can you help me to learn more?
(Another definition for texted that I've seen is " Sent message".)