Using coinage, took London Underground northwards for first time (5)
I believe the answer is:
debut
'using' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps there's a link between them I don't understand?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for debut that I've seen before include "Introduction" , "First attempt" , "First appearance, a coming-out" , "First public appearance of performer" , "Beginning, first performance" .)