Giver of guidance to one entering a scheme (5)
I believe the answer is:
pilot
'giver of guidance' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'one entering a scheme' is the wordplay.
'one' becomes 'i' (Roman numeral).
'entering' means one lot of letters goes inside another.
'a scheme' becomes 'plot' (plot is a kind of scheme).
'i' placed inside 'plot' is 'PILOT'.
'to' is the link.
Can you help me to learn more?
(Other definitions for pilot that I've seen before include "Aircraft captain" , "Small flame that ignites a gas boiler" , "Plane flyer" , "Trial broadcast" , "One-off programme" .)