Father's outside toilet, a levelled area (5)
I believe the answer is:
floor
'a levelled area' is the definition.
'father's outside toilet' is the wordplay.
'father' becomes 'fr'.
'outside' means one lot of letters goes inside another.
'toilet' becomes 'loo' (loo is a kind of toilet).
'fr' enclosing 'loo' is 'FLOOR'.
(Other definitions for floor that I've seen before include "Baffle, confound" , "Dumbfound" , "Disconcert" , "Building's base" , "Bottom surface" .)