One day going over country's proposal (10)
I believe the answer is:
nomination
'proposal' is the definition.
(thesaurus)
'one day going over country's' is the wordplay.
'one' becomes 'i' (Roman numeral).
'day' becomes 'mon' (short for Monday).
'going over' is a reversal indicator.
'country' becomes 'nation' (synonyms).
'i'+'mon'='imon'
'imon' in reverse letter order is 'nomi'.
'nomi'+'nation'='NOMINATION'
(Other definitions for nomination that I've seen before include "Naming" , "Putting forward (of a candidate)" .)