Countries, perhaps, united, behold, in ancient times (4)
I believe the answer is:
bloc
'countries perhaps united' is the definition.
(a group of associated or allied countries)
'behold in ancient times' is the wordplay.
'behold' becomes 'lo'.
'in' means one lot of letters goes inside another.
'ancient times' becomes 'bc' (Before Christ).
'lo' placed within 'bc' is 'BLOC'.
(Other definitions for bloc that I've seen before include "Alliance - coalition" , "Political group of nations" , "Allied group of countries or political parties" , "A number of countries" , "Political or economic confederation" .)