Porridge done by regular con artist (4)
I believe the answer is:
oats
'porridge done' is the definition.
I can't tell whether this defines the answer.
'regular con artist' is the wordplay.
'regular' means one should take alternating letters.
'con'+'artist'='conartist'
The alternate letters of 'conartist' are 'OATS'.
'by' is the link.
Can you help me to learn more?
(Other definitions for oats that I've seen before include "Wild ones are sown in youthful excess" , "Grain for porridge" , "Grains or porridge" , "Porridge ingredient" , "Cereal grass and seeds" .)