Mould is never upside down (7)
I believe the answer is:
inverse
'upside down' is the definition.
(I've seen this before)
'mould is never' is the wordplay.
'mould' is an anagram indicator.
'is'+'never'='isnever'
'isnever' with letters rearranged gives 'INVERSE'.
(Other definitions for inverse that I've seen before include "A direct opposite" , "Reversed in order or relation" , "Something the exact opposite of another" , "The exact opposite of enviers" , "Reversed in position like enviers" .)