Charlie lives alone in retreat for notables (7)
I believe the answer is:
colossi
'notables' is the definition.
(plural of colossus)
'charlie lives alone in retreat' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet: alpha, bravo, charlie etc.).
'lives' becomes 'is' ('be' can be a synonym of 'live').
'alone' becomes 'solo' (as in a musical solo).
'in retreat' shows that the letters should be reversed in order.
'is'+'solo'='issolo'
'issolo' written backwards gives 'olossi'.
'c'+'olossi'='COLOSSI'
'for' is the link.
(Other definitions for colossi that I've seen before include "Huge statues" , "Gigantic statues" , "Enormous statues" , "Cool sis for big people" , "powerful people" .)