How many letters does the top answer for “a piece of paper money (especially one issued by a central bank)” have?

The most common answer is banknote (8 letters).

Crossword clue: a piece of paper money (especially one issued by a central bank)

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

banknote 8 letters wn-def

a piece of paper money (especially one issued by a central bank)

greenback 9 letters wn-def

a piece of paper money (especially one issued by a central bank)