Assorted molecules as in material (13)
I believe the answer is:
miscellaneous
'assorted' is the definition.
(I know that assorted can be written as miscellaneous)
'molecules as in material' is the wordplay.
'material' indicates an anagram (the letters provide the material for a new word).
'molecules'+'as'+'in'='moleculesasin'
'moleculesasin' is an anagram of 'MISCELLANEOUS'.
(Other definitions for miscellaneous that I've seen before include "Not just one kind" , "Assorted" , "Multifarious" , "Mixed, varied" , "Sundry" .)