Support available in communist empire (4)
I believe the answer is:
stem
'support' is the definition.
(I've seen this before)
'available in communist empire' is the wordplay.
'available in' indicates the answer is hidden within the clue.
'STEM' is hidden within 'communist empire'.
(Other definitions for stem that I've seen before include "Ski turn and plant stalk" , "feature of wine glass" , "Restrain - staunch - supporter" , "Check - part of a plant" , "Stop; stalk; ship's timber" .)