Snort when there is zero writing material (4)
I believe the answer is:
oink
'snort when' is the definition.
'oink' can be an answer for 'snort' (thesaurus). I am unsure of the 'when' bit.
'zero writing material' is the wordplay.
'zero' becomes 'O' (O resembles 0).
'writing material' becomes 'ink' (substance for writing with).
'o'+'ink'='OINK'
'there is' acts as a link.
Can you help me to learn more?
(Other definitions for oink that I've seen before include "Farmyard sound" , "Noise made by a pig" , "Pig's noise" , "Piggy noise" , "Sound from a sty" .)