Ancient British tribe somewhat artistic, enigmatic (5)
I believe the answer is:
iceni
'ancient british tribe' is the definition.
(I've seen this before)
'somewhat artistic enigmatic' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'ICENI' is hidden in the letters of 'artistic enigmatic'.
(Other definitions for iceni that I've seen before include "British people once" , "East Anglian tribe of Britons" , "Ancient Brits" , "Ancient tribesmen" , "people rebelling against Rome" .)