A Gershwin and a singular artist (3)
I believe the answer is:
ira
'a gershwin' is the definition.
(lyricist Ira Gershwin, brother of George)
'a singular artist' is the wordplay.
'a singular' becomes 'i' (I can't justify this - if you can you should give a lot more credence to this answer).
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'i'+'ra'='IRA'
'and' is the link.
Can you help me to learn more?
(Other definitions for ira that I've seen before include "Songwriter George's elder brother" , "Gershwin, say" , "nationalists" , "terrorists" , "George Gershwin's older brother, the lyricist" .)