Former socialist holds flag (7)
I believe the answer is:
retired
'former' is the definition.
(eg a retired footballer is a former footballer)
'socialist holds flag' is the wordplay.
'socialist' becomes 'red' (socialism is often associated with the colour red).
'holds' indicates putting letters inside.
'flag' becomes 'tire' (I've seen this before).
'red' going around 'tire' is 'RETIRED'.
(Other definitions for retired that I've seen before include "claiming a pension?" , "In bed, withdrew" , "Went to bed or gave up work" , "Gone to bed" , "Finished work" .)