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 tell whether this definition defines the answer.
'return of bad code trashes device' is the wordplay.
'return of' is a reversal indicator.
'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' written backwards gives '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" .)