A new thing, i.e. something that isn't worn out (7)
I believe the answer is:
nightie
'something that isn't worn out' is the definition.
I can't judge whether this definition defines the answer.
'a new thing i e' is the wordplay.
'a new' indicates an anagram.
'thing' with letters rearranged gives 'night'.
'night'+'i'+'e'='NIGHTIE'
Can you help me to learn more?
(Other definitions for nightie that I've seen before include "Clothing worn in bed" , "Sleeping attire" , "Familiar bed-wear for woman" , "Bedtime wear" , "Sleepwear" .)