Communist on ship put right (7)
I believe the answer is:
'put right' is the definition.
(I've seen this before)
'communist on ship' is the wordplay.
'communist' becomes 'red' (red can informally mean communist).
'on' becomes 're' ('on' can be mean 'with reference to').
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
(Other definitions for redress that I've seen before include "set things right" , "Set right - compensation" , "Compensate" , "relief" , "Get back into gear" .)