Heard cold weather is healthy (4)
I believe the answer is:
hale
'healthy' is the definition.
(hale can mean fit and healthy)
'heard cold weather' is the wordplay.
'heard' shows a homophone (sound like).
'cold weather' becomes 'hail' (I've seen this before).
'hail' sounds like 'HALE'.
'is' is the link.
(Other definitions for hale that I've seen before include "Strong and healthy" , "Healthy and robust" , "Sound of body" , "Showing vigorous good health" , "Healthy and hearty" .)