How many letters does the top answer for “a female head of a family or tribe” have?

The most common answer is materfamilias (13 letters).

Crossword clue: a female head of a family or tribe

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

materfamilias 13 letters wn-def

a female head of a family or tribe

matriarch 9 letters wn-def

a female head of a family or tribe

the male head of family or tribe 60% similar → paterfamilias