Regular but infrequent publications from unknown, first abridged (8)
I believe the answer is:
yearlies
'regular but infrequent' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'publications from unknown first abridged' is the wordplay.
'publications from unknown' becomes 'y' (I can't explain this - if you can you should give a lot more credence to this answer).
'first' becomes 'earliest' (similar in meaning).
'abridged' means to remove the last letter.
'earliest' with its final letter taken away is 'earlies'.
'y'+'earlies'='YEARLIES'
Can you help me to learn more?
(Another definition for yearlies that I've seen is " Annuals".)