Lead in pencil is not required as artist's material (5)
I believe the answer is:
paint
'artist's material' is the definition.
(I've seen this before)
'lead in pencil is not required' is the wordplay.
'lead in' indicates taking the first letters.
'is not' becomes 'ain't' ('ain't' is a non-standard form of 'isn't').
'required' means one lot of letters go next to another.
The first letter of 'pencil' is 'p'.
'p'+'aint'='PAINT'
'as' is the link.
(Other definitions for paint that I've seen before include "Item used by 23 Across" , "Pigment" , "A pint of liquid decoration" , "Colouring substance" , "Artistic medium" .)