Understand and rescue the shipwreck victim? (4,2,5)
I believe the answer is:
take on board
Here is my best explanation:
I'm afraid I can't even guess how this answer relates to the clue.
(Other definitions for take on board that I've seen before include "Consider", "how to challenge company directors", "what chess player will often do", "opinion of directors", "accept", "Assimilate", "what press gang would do" and "Accept (new ideas)".)