Writer of Black Swan keeping completely on topic (9,3)
I believe the answer is:
ballpoint pen
'writer' is the definition.
(something which writes)
'of black swan keeping completely on topic' is the wordplay.
I cannot really see how this works, but
'of' could be 'o' and 'o' is found in the answer.
'black' could be 'b' (abbreviation as in pencil classifications) and 'b' is located in the answer.
'swan' could be 'pen' (pen is a kind of swan) and 'pen' is found within the answer.
'completely' could be 'all' (synonyms) and 'all' is found within the answer.
The remaining letters 'pint' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for ballpoint pen that I've seen before include "writer" , "Biro" .)