I see unfinished one's been accepted – they're very silly (8)

'been accepted they're very silly' is the definition.
The definition suggests an adverb but the answer is not.

'i see unfinished one's' is the wordplay.
I cannot really see how this works, but
'i' is found in the answer.
'see' could be 'c' (the word for the letter, according to Chambers) and 'c' is found within the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?