One aspect that's shelved (5)
I believe the answer is:
aside
'that's shelved' is the definition.
I can't judge whether this definition defines the answer.
'one aspect' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'aspect' becomes 'side' (side is a kind of aspect).
'a'+'side'='ASIDE'
Can you help me to learn more?
(Other definitions for aside that I've seen before include "Line spoken to the audience of a play" , "I.e. sad (anag.)" , "Out of other people's hearing" , "Actors comment to his audience" , "Stage whisper" .)