I heard a song where the singer says (emphasis added)
"I'm ready to suffer the sea"
Does it mean to make it suffer or to conquer?
It means neither "make it suffer" nor "conquer". The meaning is no. 2 in the OED:
- To go or pass through, be subjected to, undergo, experience (now usually something evil or painful).
So it means "experience the sea", implying "experience the awful things that the sea might do to me". I don't think that "suffer the sea" would be used in this way outside poetry and lyrics.