Right source of milk keeping one looking more healthy? (7)
I believe the answer is:
ruddier
'more healthy?' is the definition.
('ruddy' can be similar in meaning to 'healthy')
'right source of milk keeping one' is the wordplay.
'right' becomes 'r' (common abbreviation).
'source of milk' becomes 'udder' (eg a cow's udder).
'keeping' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'udder' going around 'i' is 'uddier'.
'r'+'uddier'='RUDDIER'
'looking' is the link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for ruddier that I've seen before include "Less white" , "Redder in complexion" , "More healthy-looking" .)