Diamonds linked with little country tribe once (5)
I believe the answer is:
iceni
'diamonds linked with little country tribe once' is the definition.
I can't judge whether this defines the answer.
'diamonds linked with little country tribe once' is the wordplay.
'diamonds' becomes 'ice' (slang term for diamonds).
'linked with' is a charade indicator (letters next to each other).
'little' means to remove the last letter (the word is not quite complete).
'country' becomes 'nz' (abbreviation for New Zealand).
'tribe once' becomes 'i' (I can't justify this - if you can you should give a lot more credence to this answer).
'nz' with its final letter taken away is 'n'.
'ice'+'n'+'i'='ICENI'
Can you help me to learn more?
(Other definitions for iceni that I've seen before include "Ancient tribesmen" , "Boadicea's tribe" , "East Anglian tribe of Britons" , "people rebelling against Rome" , "Old people" .)