Jewellery item, article collected by rising Italian artist (5)
I believe the answer is:
tiara
'jewellery item' is the definition.
'article collected by rising italian artist' is the wordplay.
'article' becomes 'a' (indefinite article).
'collected by' says to put letters next to each other (I've seen this in other clues).
'rising' says the letters should be written backwards (going up in a down clue).
'italian' becomes 'it'.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'it' in reverse letter order is 'ti'.
'a' put after 'ti' is 'tia'.
'tia'+'ra'='TIARA'
(Other definitions for tiara that I've seen before include "Jewelled head wear" , "Woman's head ornament" , "Ornamental crescent-shaped headdress or Pope's diadem" , "It might go to one's head" , "Crescent-shaped headdrsss or Pope's diadem" .)