Elegantly small double with half the joules (5)
I believe the answer is:
bijou
'elegantly small' is the definition.
'bijou' can be an answer for 'small' (I've seen this before). I am not certain of the 'elegantly' bit.
'double with half the joules' is the wordplay.
'double with' becomes 'bi' (I am not sure about this - if you are sure you should believe this answer much more).
'half the' suggests halving the letters.
'joules' halved is 'jou'.
'bi'+'jou'='BIJOU'
Can you help me to learn more?
(Other definitions for bijou that I've seen before include "Small and precious" , "Small and chic" , "item of jewellery" , "Small, elegant (from Fr.)" , "Small, but elegant and tasteful" .)