Eccentric in life, not all conform (4,4,4)
I believe the answer is:
fall into line
'conform' is the definition.
(I've seen this before)
'eccentric in life not all' is the wordplay.
'eccentric' is an anagram indicator.
'in'+'life'+'not'+'all'='inlifenotall'
'inlifenotall' is an anagram of 'FALL INTO LINE'.
(Other definitions for fall into line that I've seen before include "Dutifully conform" , "Conform with accepted behaviour" , "be conventional" .)