There's something precious in one set of twins (6)
I believe the answer is:
gemini
'set of twins' is the definition.
'gemini' can be an answer for 'twins' (I've seen this before). I'm not certain of the 'set of' bit.
'there's something precious in one' is the wordplay.
'there's' is a charade indicator (letters next to each other).
'something precious' becomes 'gem' (I can't explain this - if you can you should give a lot more credence to this answer).
'one' becomes 'i' (Roman numeral).
'gem' put next to 'in' is 'gemin'.
'gemin'+'i'='GEMINI'
Can you help me to learn more?
(Other definitions for gemini that I've seen before include "Zodiacal twins" , "star group" , "Twins constellation" , "set of twinklers" , "Zodiac sign - the Twins" .)