Small holes allowed to penetrate parts of potatoes (7)
I believe the answer is:
eyelets
'small holes' is the definition.
(I've seen this before)
'allowed to penetrate parts of potatoes' is the wordplay.
'allowed' becomes 'let' (I've seen this before).
'to penetrate' indicates putting letters inside.
'parts of potatoes' becomes 'eyes' (I can't justify this - if you can you should give a lot more credence to this answer).
'let' placed within 'eyes' is 'EYELETS'.
Can you help me to learn more?
(Other definitions for eyelets that I've seen before include "peep-holes" , "Rings for reinforcement" , "Small holes" .)