Kind of wine regularly sampled at source, it's noted (4,5)

'it's noted' is the definition.
(I've seen this before)

'kind of wine regularly sampled at source' is the wordplay.
'regularly sampled' indicates alternate letters.
'at' is a charade indicator (letters next to each other) (I've seen this in other clues).
'source' becomes 'well' (well is a kind of source).
'kind'+'of'+'wine'='kindofwine'
The alternating letters of 'kindofwine' are 'known'.
'known' after 'well' is 'WELL-KNOWN'.