One entering cross country? (5)
I believe the answer is:
spain
'country?' is the definition.
(Spain is an example)
'one entering cross' is the wordplay.
'one' becomes 'i' (Roman numeral).
'entering' is an insertion indicator.
'cross' becomes 'span' ('span' can be a synonym of 'cross'**).
'i' put within 'span' is 'SPAIN'.
(Other definitions for spain that I've seen before include "holiday destination?" , "Catholic country" , "Iberian 4" , "Kingdom" , "country of mostly dry mountains, going by air" .)