Pseud sacked by bureau ultimately finished (4,2)
I believe the answer is:
used up
'finished' is the definition.
(I've seen this before)
'pseud sacked by bureau ultimately' is the wordplay.
'sacked' indicates an anagram (sack can mean to destroy).
'by' says to put letters next to each other.
'ultimately' indicates one should take the final letters.
The last letter of 'bureau' is 'u'.
'pseud' anagrammed gives 'sedup'.
'sedup' after 'u' is 'USED-UP'.
(Other definitions for used up that I've seen before include "Exhausted the supply" , "Consumed completely" , "Spent" , "Consumed, finished" .)