Vegetable one cut twice, I accepted (5)
I believe the answer is:
onion
'vegetable' is the definition.
(onion is a vegetable)
'one cut twice i accepted' is the wordplay.
'twice i' means two replacements for 'i'.
'one' becomes 'on' (I can't explain this - if you can you should give a lot more credence to this answer).
'cut' means to remove the last letter.
'i' becomes 'one' (Roman numeral for one).
'accepted' is an insertion indicator.
'one' with its last letter removed is 'on'.
'on'+'on'='onon'
'onon' placed around 'i' is 'ONION'.
Can you help me to learn more?
(Other definitions for onion that I've seen before include "Aromatic flavourful versatile vegetable" , "Head (slang); vegetable" , "reason for tears" , "Pungent vegetable" , "associated with 26 [TRIPE] ?" .)