Fixed a mess by foreign ministry (7)
I believe the answer is:
embassy
'foreign ministry' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe there's a link between them I don't understand?
'fixed a mess by' is the wordplay.
'fixed' indicates anagramming the letters.
'a'+'mess'+'by'='amessby'
'amessby' with letters rearranged gives 'EMBASSY'.
Can you help me to learn more?
(Other definitions for embassy that I've seen before include "Diplomatic office or residence." , "foreign mission abroad" , "Ambassador's office" , "diplomatic venue" , "Overseas mission" .)