Expose former head of state with looming disaster overhanging a one-time country (5,8)
I believe the answer is:
outer mongolia
'a one-time country' is the definition.
'Outer Mongolia' can be an answer for 'country' (Outer Mongolia is an example). I am not sure about the 'a one-time' bit.
'expose former head of state with looming disaster overhanging' is the wordplay.
'expose' becomes 'out' (to out someone is to expose them).
'former head of state' becomes 'ER' (Elizabeth Regina, ie Queen Elizabeth).
'with' says to put letters next to each other.
'disaster' indicates anagramming the letters.
'overhanging' becomes 'a' (I can't explain this - if you can you should believe this answer much more).
'looming' with letters rearranged gives 'mongoli'.
'out'+'er'+'mongoli'+'a'='OUTER MONGOLIA'
Can you help me to learn more?
(Other definitions for outer mongolia that I've seen before include "Former Asian state" , "Country" .)