How do you pronounce the word deficience in french?

The word "deficience" doesn't exist in French. It's a misspelling of the French word "déficience", which is pronounced:

deh-fee-si-ahns

* deh: like the "day" in "daybreak"

* fee: like the "fee" in "feeble"

* si: like the "see" in "seeing"

* ahns: like the "on" in "gone", but with a slightly longer sound

Therefore, "déficience" in French is pronounced "deh-fee-si-ahns."