Continue playing a role somewhere in West London (5)
I believe the answer is:
Here is my best explanation:
'somewhere in west london' is the definition.
'continue playing a role' is the subsidiary indication.
I cannot really see how this works, but
'continue' could be 'on' (I've seen this in other clues) and 'on' is present in the answer.
'a' is present in the answer.
This explanation may well be incorrect...
(Other definitions for acton that I've seen before include "Part of the London borough of Ealing - British historian, d. 1902", "English statesman", "somewhere in London", "Gladstone's adviser", "District of West London", "London area", "Respond in accordance with - London district" and "part of London on the tube".)