I am into Italian writer — sparkling stuff (8)
I believe the answer is:
diamante
'sparkling stuff' is the definition.
(sparkly jewellery)
'i am into italian writer' is the wordplay.
'into' indicates putting letters inside.
'italian writer' becomes 'Dante' (Italian poet).
'i'+'am'='iam'
'iam' going into 'dante' is 'DIAMANTE'.
(Other definitions for diamante that I've seen before include "Animated, being decorated with sparkling substance" , "Glittering decoration" , "Rhinestone-covered" , "Decorated with glass to imitate gems" , "Glittering fabric or costume jewellery" .)