Backing last couple of actors in show (8)
I believe the answer is:
reversal
'backing last' is the definition.
'reversal' can be an answer for 'backing' (thesaurus). I'm not sure about the 'last' bit.
'couple of actors in show' is the wordplay.
'couple of actors' becomes 'rs' (I am not sure about this - if you are sure you should believe this answer much more).
'in' indicates putting letters inside.
'show' becomes 'reveal' (revealing is a kind of showing).
'rs' going into 'reveal' is 'REVERSAL'.
Can you help me to learn more?
(Other definitions for reversal that I've seen before include "A change to an opposite direction" , "switch" , "A turning back" , "misfortune!" , "Negation" .)