It means good health to a drinker (5)

'it means good health' is the definition.
The definition suggests a singular noun but the answer is not.

'a drinker' is the wordplay.
I cannot quite see how this works, but
'a' is found in the answer.
The remaining letters 'skol' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'to' acts as a link.

Can you help me to learn more?