Everything not encoded in signal (3,5)
I believe the answer is:
all clear
'signal' is the definition.
(all clear is a kind of signal)
'everything not encoded' is the wordplay.
'everything' becomes 'all' (all things).
'not encoded' becomes 'clear' (I can't explain this - if you can you should give a lot more credence to this answer).
'all'+'clear'='ALL-CLEAR'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for all clear that I've seen before include "Siren sound to mark end of bombing by planes" , "Signal danger is ended" , "with absolutely no ambiguity" , "Signal that danger is past" , "Permission to proceed" .)