Friendly nation taking part in Eton game (5)
I believe the answer is:
tonga
'friendly nation' is the definition.
'Tonga' can be an answer for 'nation' (Tonga is an example). I'm not sure about the 'friendly' bit.
'part in eton game' is the wordplay.
'part in' indicates the answer is hidden within the clue.
'TONGA' is hidden in the letters of 'eton game'.
'taking' is the link.
Can you help me to learn more?
(Other definitions for tonga that I've seen before include "Horse-drawn vehicle" , "Pacific island kingdom" , "S.W Pacific Kingdom" , "Pacific island state" , "Two-wheeled Indian vehicle" .)