Article appearing in Echo after Thursday (3)
I believe the answer is:
the
'article' is the definition.
(the 'definite article' part of speech)
'echo after thursday' is the wordplay.
'echo' becomes 'e' (phonetic alphabet: alpha, bravo, charlie etc.).
'after' is a charade indicator (letters next to each other).
'thursday' becomes 'th' ('Th' can be a synonym of 'thursday').
'e' put after 'th' is 'THE'.
'appearing in' is the link.
(Other definitions for the that I've seen before include "Last words of story" , "SECOND PART OF 23" , "Finis" , "and 24 Down: Similar things" , "The most frequently occurring word in the Bible (and in this clue!)" .)