Coat on back of plump actor (6)
I believe the answer is:
player
'actor' is the definition.
(synonyms)
'coat on back of plump' is the wordplay.
'coat' becomes 'layer' (layering is a kind of coating).
'on' is a charade indicator (letters next to each other).
'back of plump' becomes 'p' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'layer' after 'p' is 'PLAYER'.
Can you help me to learn more?
(Other definitions for player that I've seen before include "Game's participant" , "South African golfer, Gary" , "Sportsman - instrumentalist" , "Contestant" , "Batsman perhaps" .)