Return of bad code trashes device (7)
I believe the answer is:
gubbins
'return of bad code trashes device' is the definition.
I can't judge whether this defines the answer.
'return of bad code trashes device' is the wordplay.
'return of' shows that the letters should be reversed in order.
'bad code trashes' becomes 'snib' (I can't justify this - if you can you should give a lot more credence to this answer).
'device' becomes 'bug' (bug is a kind of device).
'snib'+'bug'='snibbug'
'snibbug' backwards is 'GUBBINS'.
Can you help me to learn more?
(Other definitions for gubbins that I've seen before include "Paraphernalia" , "Trivial object - silly person" , "something worthless" , "Odds and ends - litter" , "Trivial object or gadget" .)