Country welcomed by Washington, Gambia (5)
I believe the answer is:
tonga
'country' is the definition.
(Tonga is an example)
'welcomed by washington gambia' is the wordplay.
'welcomed by' indicates a hidden word.
'TONGA' is hidden in the letters of 'washington gambia'.
(Other definitions for tonga that I've seen before include "group of Pacific islands" , "transport" , "two-wheeler" , "Pacific Ocean monarchy" , "Tropic island" .)