Aberrant, erratic emphasis placed on noun (9)
I believe the answer is:
misshapen
'aberrant' is the definition.
(both can mean abnormal or irregular)
'erratic emphasis placed on noun' is the wordplay.
'erratic' indicates anagramming the letters.
'placed on' means one lot of letters go next to another.
'noun' becomes 'n'.
'emphasis' anagrammed gives 'misshape'.
'misshape'+'n'='MISSHAPEN'
(Other definitions for misshapen that I've seen before include "Badly designed" , "Distorted" , "Deformed" , "Ugly in form" , "Not looking round" .)