Front of building roughly covered with flag (6)
I believe the answer is:
facade
'front of building' is the definition.
(I've seen this before)
'roughly covered with flag' is the wordplay.
'roughly' becomes 'ca' (abbreviation for circa).
'covered with' means one lot of letters goes inside another.
'flag' becomes 'fade' (I've seen this in another clue).
'ca' inserted within 'fade' is 'FACADE'.
(Other definitions for facade that I've seen before include "(False) outward appearance" , "Outside of a building" , "False front" , "Front-of-house" , "Walton's setting of Sitwell's verses" .)