Estate agent maybe before succeeded with singular printing method (11)
I believe the answer is:
letterpress
'printing method' is the definition.
(letterpress is a printing technique)
'estate agent maybe before succeeded with singular' is the wordplay.
'estate agent maybe' becomes 'letter' (an estate agent might let property).
'before' becomes 'pre' (prefix meaning 'before').
'succeeded' becomes 's' (genealogical abbreviation).
'with' means one lot of letters go next to another.
'singular' becomes 's' (abbreviation sometimes used in dictionaries).
'letter'+'pre'+'s'+'s'='LETTERPRESS'
(Other definitions for letterpress that I've seen before include "Text, not illustrations; printing from raised type" , "reading matter" , "Printing technique" .)