Cart off desk first - that's official (10)
I believe the answer is:
bureaucrat
'that's official' is the definition.
(a bureaucrat is a government official)
'cart off desk first' is the wordplay.
'off' indicates anagramming the letters.
'desk' becomes 'bureau' (type of writing desk).
'first' means one lot of letters go next to another.
'cart' is an anagram of 'crat'.
'crat' after 'bureau' is 'BUREAUCRAT'.
(Other definitions for bureaucrat that I've seen before include "Mandarin" , "Government official" , "Administrator" .)