Not working at that point with my department (unofficially) (3,3,6)
I believe the answer is:
off the record
'unofficially' is the definition.
(I've seen this before)
'not working at that point with my department' is the wordplay.
'not working' becomes 'off' (I've seen this before).
'at that point' becomes 'there' (over there).
'with' says to put letters next to each other.
'my' becomes 'cor' (both are expressions of surprise).
'department' becomes 'd' (abbreviation eg in MOD Ministry of Defence).
'off'+'there'+'cor'+'d'='OFF-THE-RECORD'
(Other definitions for off the record that I've seen before include "in private" , "not to be broadcast" , "What you take when the disc finishes" , "Where the rejected tracks are kept" , "Sub rosa" .)