Start with SUB and add the word described by the first clue to get the word described by the second clue.
-1. SUB + harden = Part of a bigger group. 6 letters
-2. SUB + quest = The act of yielding to another. 10
-3. SUB + to message someone using a cellphone = Nuance or undertone. 7
4. SUB + a piece of land = To deduct. 8
5. SUB + posture = Matter. 9
6. SUB + edge = To sink. 7
7. SUB + a citrus fruit = Transcendent. 7
-8. SUB + a letter = Docile. 10
9. SUB + a seaman = Underwater. 9
-10. SUB + to combine = To go under the surface. 8
