Novelist retaining hard copy (4)
I believe the answer is:
Here is my best explanation:
'copy' is the definition.
'novelist retaining hard' is the wordplay.
'novelist' becomes 'eco' (Umberto Eco).
'retaining' means one lot of letters goes inside another.
'hard' becomes 'h'.
'eco' going around 'h' is 'ECHO'.
(Other definitions for echo that I've seen before include "Reverberate - nymph spurned by Narcissus", "next to delta", "Nymph (only able to repeat the last words of others)", "from Brussels?", "Nymph; E (radio comms.)", "repercussion", "Sound reflection", "Reiterate", "Marked by heat" and "Imitate -- a nymph".)