Healthy source of water (4)
I believe the answer is:
well
I believe this is a double definition.
'healthy' is the first definition.
(similar in meaning)
'source of water' is the second definition.
(water may come from a well)
(Other definitions for well that I've seen before include "Competently" , "Fine - drilled hole" , "Bore; extremely" , "Very; without difficulty; bore" , "Flow up" .)