Greek storyteller making front of audience sit up (5)
I believe the answer is:
aesop
'greek storyteller' is the definition.
(I've seen this before)
'front of audience sit up' is the wordplay.
'front of' indicates taking the first letters (the letter at the front of the word).
'sit' becomes 'pose' (as in sitting for a painter).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
The first letter of 'audience' is 'a'.
'pose' back-to-front is 'esop'.
'a'+'esop'='AESOP'
'making' is the link.
(Other definitions for aesop that I've seen before include "Greek storyteller" , "Fabulous writer" , "A pose of famed fable teller" , "Greek fabulist (Tortoise and the Hare)" , "he wrote in Greek" .)