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 defines the answer.
'return of bad code trashes device' is the wordplay.
'return of' says the letters should be written in reverse.
'bad code trashes' becomes 'snib' (I can't explain this - if you can you should believe this answer much more).
'device' becomes 'bug' (bug is a kind of device).
'snib'+'bug'='snibbug'
'snibbug' back-to-front 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" .)