Hundreds taking time on motorway in China (7)
I believe the answer is:
ceramic
'china' is the definition.
(I've seen this before)
'hundreds taking time on motorway' is the wordplay.
'hundreds' becomes 'cc' (the Roman numeral for a hundred written twice).
'taking' is an insertion indicator.
'time' becomes 'era' (an era is a period of time).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'motorway' becomes 'MI' (resembles Me, English motorway).
'era'+'mi'='erami'
'cc' enclosing 'erami' is 'CERAMIC'.
'in' acts as a link.
(Other definitions for ceramic that I've seen before include "Earthenware" , "Pottery material or product" , "Potter's product" , "china bowl, say" , "Brittle material of baked clay" .)