He turned up with a letter for Nora (5)
I believe the answer is:
aaron
'he turned' is the definition.
The definition suggests a singular noun which matches the answer.
'up with a letter for nora' is the wordplay.
'up with' is a reversal indicator (move letters in down clue up).
'a letter' becomes 'a'.
'for' says to put letters next to each other (I've seen this in other clues).
'a' after 'nora' is 'noraa'.
'noraa' back-to-front is 'AARON'.
Can you help me to learn more?
(Other definitions for aaron that I've seen before include "Brother of Moses, led the Jews to the Promised Land" , "- - Copland (mus.)" , "Boy" , "Brother of Moses and traditional founder of Jewish priesthood" , "Bearded fellow" .)