How many letters does the top answer for “relating to or located below the epidermis” have?

The most common answer is hypodermic (10 letters).

Crossword clue: relating to or located below the epidermis

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

hypodermic 10 letters wn-def

a piston syringe that is fitted with a hypodermic needle for giving injections

subcutaneous 12 letters wn-def

relating to or located below the epidermis