Would the herbalist wish he hadn't stocked it? (3)
I believe the answer is:
rue
'would the herbalist wish he hadn't' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'stocked it?' is the wordplay.
'stocked' becomes 'ru' (I can't justify this - if you can you should give a lot more credence to this answer).
'it?' becomes 'e' ('e' can mean 'electronic' which is similar to 'IT').
'ru'+'e'='RUE'
Can you help me to learn more?
(Other definitions for rue that I've seen before include "Regret - wild shrub" , "Regret; road (Fr.)" , "show regret" , "Feel remorse" , "Lament; a herb" .)