Answer: hartshorn

AnswerCrossword Clue
HARTSHORNAntler.
HARTSHORNDeer's antler
hartshornthe antler of a hart, formerly used as a source of ammonia
hartshornammonium carbonate
hartshornthe horn or antler of a hart; the substance obtained by rasping, slicing, or calcining this, formerly the chief source of ammonia