Joe's guarding controversial artist's The Twins (6)
I believe the answer is:
gemini
'the twins' is the definition.
(I've seen this in another clue)
'joe's guarding controversial artist's' is the wordplay.
'joe' becomes 'GI' (GI Joe).
'guarding' is an insertion indicator.
'controversial artist' becomes 'emin' (I've seen this before. I am not sure about the 'controversial' bit.).
'gi' going around 'emin' is 'GEMINI'.
Can you help me to learn more?
(Other definitions for gemini that I've seen before include "Twins star-sign" , "lot of stars" , "Third sign of the Zodiac" , "set of twinklers" , "star group" .)