Slang is back in signs giving information (7)
I believe the answer is:
signals
'signs giving information' is the definition.
'signals' can be an answer for 'signs' ('signal' can be a synonym of 'sign'). I'm not sure about the 'giving information' bit.
'slang is back' is the wordplay.
'back' shows that the letters should be reversed in order.
'slang'+'is'='slangis'
'slangis' reversed gives 'SIGNALS'.
'in' is the link.
Can you help me to learn more?
(Other definitions for signals that I've seen before include "Actions that encode messages" , "Coded communications" , "Flags, gestures" , "Indications or gestures as information or warning" , "(Traffic) lights" .)