The PR beat-up overwhelms a performer (8)
I believe the answer is:
thespian
'performer' is the definition.
(I know that thespian is a type of performer)
'the pr beat-up overwhelms a' is the wordplay.
'pr beat' becomes 'nips' (I can't explain this - if you can you should believe this answer much more).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'overwhelms' indicates putting letters inside.
'nips' back-to-front is 'spin'.
'spin' placed around 'a' is 'spian'.
'the'+'spian'='THESPIAN'
Can you help me to learn more?
(Other definitions for thespian that I've seen before include "stage performer" , "Dramatic actor" , "Actor - neat hips (anag)" , "Relating to the theatre" , "Stage actor" .)