Attractive hard copy kept in secret (7)
I believe the answer is:
shapely
'attractive' is the definition.
(shapely means attractive or elegant)
'hard copy kept in secret' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'copy' becomes 'ape' (ape can mean to copy or imitate).
'kept in' means one lot of letters goes inside another.
'secret' becomes 'sly' (I've seen this in other clues).
'h'+'ape'='hape'
'hape' inserted within 'sly' is 'SHAPELY'.
(Other definitions for shapely that I've seen before include "Attractively proportioned" , "Pleasingly formed" , "Well-turned" , "Looking good?" , "Well-proportioned" .)