Brilliant twins coming to a bad end (5)
I believe the answer is:
vivid
'brilliant' is the definition.
(synonyms)
'twins coming to a bad end' is the wordplay.
'twins coming' becomes 'vivi' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'end' indicates one should take the final letters.
The last letter of 'bad' is 'd'.
'vivi'+'d'='VIVID'
Can you help me to learn more?
(Other definitions for vivid that I've seen before include "Intense" , "Lifelike, striking" , "Intensely striking in colour" , "Intensely deep/bright" , "Brilliantly coloured - full of life" .)