Indefinable quality journalist illustrated originally about Oasis and Queen performing (2,2,4,4)
I believe the answer is:
je ne sais quoi
'indefinable quality' is the definition.
(I've seen this before)
'journalist illustrated originally about oasis and queen performing' is the wordplay.
'originally' says to take the initial letters.
'about' means one lot of letters goes inside another.
'and' says to put letters next to each other.
'performing' is an anagram indicator.
The first letters of 'journalist illustrated' is 'ji'.
'oasis'+'queen'='oasisqueen'
'oasisqueen' is an anagram of 'enesaisquo'.
'ji' placed around 'enesaisquo' is 'JE NE SAIS QUOI'.
(Other definitions for je ne sais quoi that I've seen before include "Indescribable quality" , "Special unknown ingredient" , "Something indescribable (French)" , "Quality or thing that's hard to describe" , "Quality that can't be easily described" .)