Sid back on track in speech (9)
I believe the answer is:
discourse
'speech' is the definition.
(discourse is a kind of speech)
'sid back on track' is the wordplay.
'back' says the letters should be written in reverse.
'on' means one lot of letters go next to another.
'track' becomes 'course' ('course' can be a synonym of 'track'**).
'sid' written backwards gives 'dis'.
'dis'+'course'='DISCOURSE'
'in' acts as a link.
(Other definitions for discourse that I've seen before include "Written or spoken communication" , "verbal communication" , "Speech - conversation" , "Communication verbally" , "To hold a conversation" .)