Smear son -- isn't one person without any faults apparently (7,5)
I believe the answer is:
plaster saint
'one person without any faults apparently' is the definition.
I can't judge whether this defines the answer.
'smear son isn't' is the wordplay.
'smear' becomes 'plaster' (I've seen this before).
'son' becomes 's' (genealogical abbreviation for son).
'isn't' becomes 'aint' (non-standard version of 'isn't').
'plaster'+'s'+'aint'='PLASTER SAINT'
Can you help me to learn more?
(Other definitions for plaster saint that I've seen before include "One not as good as they would seem" , "Hypocritical goody-goody" .)