Letter Goethe tantalisingly conceals (5)
I believe the answer is:
theta
'letter' is the definition.
(Greek letter)
'goethe tantalisingly conceals' is the wordplay.
'conceals' indicates the answer is hidden within the clue.
'THETA' is hidden within 'goethe tantalisingly'.
(Other definitions for theta that I've seen before include "Make amends for" , "classic character?" , "character in Euripides" , "Letter before iota" , "Homeric character" .)