In addition, one left, such has been stated (4)
I believe the answer is:
also
'in addition' is the definition.
(synonyms)
'one left such has been stated' is the wordplay.
I cannot really understand how this works, but
'one' could be 'a' (a thing is one thing) and 'a' is present in the answer.
'left' could be 'l' (common abbreviation) and 'l' is present in the answer.
'such' could be 'so' and 'so' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for also that I've seen before include "revolutionary a part for Yugoslavia" , "As well, in addition" , "To boot" , "item's rarely used now for this" , "Additionally" .)