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 a hidden word.
'ANDES' is hidden within '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" .)