Heard of mark on potato publication (9)
I believe the answer is:
spectator
'publication' is the definition.
(the Spectator is a magazine)
'heard of mark on potato' is the wordplay.
I cannot quite understand how this works, but
'heard' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
'of' could be 'o' and 'o' is found within the answer.
'on' could be 'at' (I've seen this in other clues) and 'at' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for spectator that I've seen before include "Person watching" , "Onlooker at game" , "Onlooker; magazine" , "Part of gate" , "I attend sporting event" .)