Empire in complete mess at the outset (5)
I believe the answer is:
realm
'empire' is the definition.
(I've seen this in another clue)
'complete mess at the outset' is the wordplay.
'complete' becomes 'real' (I've seen this in another clue).
'at the outset' suggests taking the first letters (the outset is the beginning).
The initial letter of 'mess' is 'm'.
'real'+'m'='REALM'
'in' acts as a link.
(Other definitions for realm that I've seen before include "Area of influence" , "Kingdom could be lamer" , "Area of interest/activity" , "Royal domain" , "Country" .)