Manage a day with head of government department (10)
I believe the answer is:
administer
'manage' is the definition.
(I know that manage is a kind of administer)
'a day with head of government department' is the wordplay.
'day' becomes 'd' (abbreviation for day).
'with' means one lot of letters go next to another.
'head of government department' becomes 'minister' (I've seen this before).
'a'+'d'+'minister'='ADMINISTER'
(Other definitions for administer that I've seen before include "man?" , "Handle" , "give" , "act as manager" , "Manage" .)