How many letters does the top answer for “making susceptible or sensitive to either physical or emotional stimuli” have?

The most common answer is sensitising (11 letters).

Crossword clue: making susceptible or sensitive to either physical or emotional stimuli

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

sensitising 11 letters wn-def

rendering an organism sensitive to a serum by a series of injections

sensitizing 11 letters wn-def

rendering an organism sensitive to a serum by a series of injections