Instruction from Berlin? Fool around on army time (6)
I believe the answer is:
diktat
'instruction from berlin?' is the definition.
(German term for a decree from authority)
'fool around on army time' is the wordplay.
'fool' becomes 'kid' (kidding is a kind of fooling**).
'around' shows that the letters should be reversed in order.
'on' means one lot of letters go next to another.
'army' becomes 'ta' (abbreviation for Territorial Army).
'time' becomes 't'.
'kid' backwards is 'dik'.
'dik'+'ta'+'t'='DIKTAT'
(Other definitions for diktat that I've seen before include "Harsh order, allowing no discussion" , "Harsh order given by someone with authority" , "An order that allows no opposition" , "Forceful order that must be obeyed" , "Official order" .)