Countries left with resources last (5)
I believe the answer is:
lands
'countries' is the definition.
(I know this)
'left with resources last' is the wordplay.
'left' becomes 'l' (common abbreviation).
'with' becomes 'and'.
'last' says to take the final letters.
The final letter of 'resources' is 's'.
'l'+'and'+'s'='LANDS'
(Other definitions for lands that I've seen before include "Alights" , "See 21" , "Obtains" , "Comes ashore" .)