Strike sees one leaving London area (5)
I believe the answer is:
'london area' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for acton that I've seen before include "part of London on the tube" , "Gladstone's adviser" , "District of West London" , "somewhere in London" , "London area" .)