Dismissed, if turning communist (5)
I believe the answer is:
fired
'dismissed' is the definition.
(synonyms)
'if turning communist' is the wordplay.
'turning' says the letters should be written in reverse.
'communist' becomes 'red' (red can informally mean communist).
'if' in reverse letter order is 'fi'.
'fi'+'red'='FIRED'
(Other definitions for fired that I've seen before include "Dismissed; set off" , "(Of pottery) baked" , "got rid of" , "Encouraged" , "Set ablaze" .)