Watchful, warm hearted fellow (5)
I believe the answer is:
argus
But I can't explain it at all! Could you help me understand?
(Other definitions for argus that I've seen before include "Alert watchman" , "Greek giant with 100 eyes" , "Small butterfly" , "In Greek myth, a many-eyed monster slain by Hermes" , "Giant with one hundred eyes in Greek mythology" .)