This is the 2642nd most frequent German word.
deutscher
"Deutscher" means "German (male)" in English.
Here, 'deutscher' is used as an adjective modifying 'Schriftsteller' (writer), indicating the nationality and quality.
Er ist ein deutscher Schriftsteller.
He is a German writer.
In this sentence, 'Deutscher' is used as a noun, specifically referring to a person from Germany.
Peter ist ein Deutscher.
Peter is a German.
'Deutsche' or 'deutsches' is used here as an adjective modifying 'Bier' (beer), emphasizing its origin.