Sacked if turning socialist (5)
I believe the answer is:
fired
'sacked' is the definition.
(both can mean dismissed from a job)
'if turning socialist' is the wordplay.
'turning' says the letters should be written backwards.
'socialist' becomes 'red' (socialism is often associated with the colour red).
'if' written backwards gives 'fi'.
'fi'+'red'='FIRED'
(Other definitions for fired that I've seen before include "Set ablaze" , "with P45?" , "Encouraged" , "Dismissed or ignited" , "(Of pottery) baked" .)