How many letters does the top answer for “on or coming from the other side of the mountains (from the speaker)” have?

The most common answer is tramontane (10 letters).

Crossword clue: on or coming from the other side of the mountains (from the speaker)

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

tramontane 10 letters wn-def

a cold dry wind that blows south out of the mountains into Italy and the western Mediterranean

transmontane 12 letters wn-def

on or coming from the other side of the mountains (from the speaker)