While 深い (ふかい) means "profound; deep; dense", 箆 (へら, の), as a noun, means "spatula; arrow shaft" in japanese and, originally, "fine-toothed comb" in chinese.
This word is used adverbially in this sentence:
箆深く射された矢がなかった。
箆深く could mean something like "deep as an arrow" or "arrow-like deep", but would it not be redundant if it appears before 矢?