How many letters does the top answer for “a former english silver coin worth four pennies” have?

The most common answer is fourpence (9 letters).

Crossword clue: a former english silver coin worth four pennies

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

fourpence 9 letters wn-def

a former English silver coin worth four pennies

groat 5 letters wn-def

a former English silver coin worth four pennies

an english coin worth half a penny 50% similar → halfpenny