Populous centre of Acton, now rebuilt (4)
I believe the answer is:
town
'populous centre' is the definition.
'town' can be an answer for 'centre' (I have seen 'Centre of population' mean 'town' so perhaps 'centre' could also mean 'town'). I'm not certain of the 'populous' bit.
'acton now rebuilt' is the wordplay.
'acton' becomes 't' (I can't explain this - if you can you should believe this answer much more).
'rebuilt' indicates an anagram.
'now' is an anagram of 'own'.
't'+'own'='TOWN'
'of' is the link.
Can you help me to learn more?
(Other definitions for town that I've seen before include "Milton Keynes, say, with 1a [NEW]" , "Municipality" , "Densely populated area" , "Nelson, for example" , "eg Ripley" .)