Flipping insubstantial parts I'm going to name Olivia or Orsino? (8)
I believe the answer is:
'olivia or orsino?' is the definition.
(I know that Olivia is a Illyrian)
'flipping insubstantial parts i'm going to name' is the wordplay.
'flipping' shows that the letters should be reversed in order.
'insubstantial' becomes 'airy' (similar in meaning).
'parts' is an insertion indicator (in the sense of cuts or separates).
'i'm going to' becomes 'I'll' ('I'm going to' can mean 'I will' or 'I'll').
'name' becomes 'n' (common abbreviation e.g. on forms).
'airy' in reverse letter order is 'yria'.
'yria' put inside 'illn' is 'ILLYRIAN'.
(Other definitions for illyrian that I've seen before include "old foreign language" , "language from Albania" .)