Top shearer follows red-backed gun (9)
I believe the answer is:
derringer
'gun' is the definition.
(I know that Derringer is a type of pistol)
'top shearer follows red-backed' is the wordplay.
'top shearer' becomes 'ringer' (I am not sure about this - if you are sure you should believe this answer much more).
'follows' means one lot of letters go next to another.
'backed' says the letters should be written in reverse.
'red' back-to-front is 'der'.
'ringer' after 'der' is 'DERRINGER'.
Can you help me to learn more?
(Other definitions for derringer that I've seen before include "Weapon" , "Pocket pistol" , "Small pistol used by gamblers in western films" , "Short-barrelled American pistol" .)