Diarist scribbled after snake plant (10)
I believe the answer is:
aspidistra
'plant' is the definition.
(aspidistra is a kind of plant)
'diarist scribbled after snake' is the wordplay.
'scribbled' indicates anagramming the letters (I've seen this in other clues).
'after' means one lot of letters go next to another.
'snake' becomes 'asp' (asp is a kind of snake).
'diarist' with letters rearranged gives 'idistra'.
'idistra' put after 'asp' is 'ASPIDISTRA'.
(Other definitions for aspidistra that I've seen before include "something normally developed in-house?" , "For Asian native" , "Household growth" , "Houseplant of lily family" , "The biggest - (in the world) (Gracie Fields)" .)