Old coin, article blocking pipe? (5)
I believe the answer is:
ducat
'old coin' is the definition.
(I've seen this before)
'article blocking pipe?' is the wordplay.
'article' becomes 'a' (the indefinite article in English).
'blocking' indicates putting letters inside (block can mean to plug a gap in something).
'pipe?' becomes 'duct' (I've seen this in another clue).
'a' placed into 'duct' is 'DUCAT'.
(Other definitions for ducat that I've seen before include "Former Eur. gold coin" , "Antique coin" , "Money no longer" , "Ancient coin" , "ready no longer" .)