Part of Italian designer's range (5)
I believe the answer is:
andes
'range' is the definition.
(South American mountain range)
'part of italian designer's' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'ANDES' is hidden in the letters of 'italian designers'.
(Other definitions for andes that I've seen before include "Peak District" , "World's longest mountain range" , "Aconcagua the highest in this range" , "Major mountain range" , "danes found in mountains" .)