Friend in French department — Hannah, possibly (10)
I believe the answer is:
palindrome
'friend in french department hannah possibly' is the definition.
I can't judge whether this definition defines the answer.
'friend in french department hannah possibly' is the wordplay.
'friend' becomes 'pal' (pal can mean a friend).
'in' is an insertion indicator.
'french department' becomes 'indre' (I've seen this before).
'hannah possibly' becomes 'om' (I can't explain this - if you can you should give a lot more credence to this answer).
'indre' placed around 'om' is 'indrome'.
'pal'+'indrome'='PALINDROME'
Can you help me to learn more?
(Other definitions for palindrome that I've seen before include "Word like the Indian language "Malayalam", for instance" , "Word reading same forwards and back" , "Word as kayak, refer" , "Mum, Dad or Sis" , "which looks the same from the other side" .)