Forbidden to display sphere (3)
I believe the answer is:
orb
'sphere' is the definition.
(I know that orb is a type of sphere)
'forbidden to display' is the wordplay.
'to display' indicates a hidden word (I've seen 'displaying' mean this).
'ORB' can be found hidden inside 'forbidden'.
(Other definitions for orb that I've seen before include "Sphere (found in regalia)" , "Sphere - eye" , "A poetic eye, bro" , "Ring" , "Celestial body; sphere" .)