Are designed then made of clay (7)
I believe the answer is:
earthen
'made of clay' is the definition.
(I've seen this in another clue)
'are designed then' is the wordplay.
'designed' indicates an anagram (designed with the letters).
'are' with letters rearranged gives 'ear'.
'ear'+'then'='EARTHEN'
(Other definitions for earthen that I've seen before include "of the soil" , "that's thrown in clay" , "Made of baked clay, perhaps ware" , "(Of pot) made of baked clay" , "from the ground" .)