Manly Beach - regularly a slum in disarray (9)
I believe the answer is:
masculine
'manly' is the definition.
(associated in meaning)
'beach regularly a slum in disarray' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'disarray' is an anagram indicator.
The alternating letters of 'beach' are 'ec'.
'ec'+'a'+'slum'+'in'='ecaslumin'
'ecaslumin' with letters rearranged gives 'MASCULINE'.
(Other definitions for masculine that I've seen before include "Butch" , "Possessing qualities of a man" , ""Man" is clue (anag)" , "Calumnies about macho type" , "Calumnies about male equality" .)