Preserves not a word that's in writing (7)
I believe the answer is:
mummies
'preserves' is the definition.
Although both the answer and definition are plural nouns, I don't understand how one could define the other.
'not a word that's in writing' is the wordplay.
'not a word' becomes 'mum' (I've seen this before).
'that's' becomes 'ie'.
'in' means one lot of letters goes inside another.
'writing' becomes 'MS' (abbreviation for manuscript).
'ie' going into 'ms' is 'mies'.
'mum'+'mies'='MUMMIES'
Can you help me to learn more?
(Another definition for mummies that I've seen is " Informal mothers or preserved Pharaohs".)