Downtrodden worker keeping a promise (6)
I believe the answer is:
parole
'promise' is the definition.
(I know that parole is a type of promise)
'downtrodden worker keeping a' is the wordplay.
'downtrodden worker' becomes 'prole' (member of proletariat class).
'keeping' indicates putting letters inside.
'prole' enclosing 'a' is 'PAROLE'.
(Other definitions for parole that I've seen before include "Promise (that prisoner is released on)" , "Promise of not escaping etc" , "Release of prisoner promising good behaviour" , "Word - condition of liberty" , "Promise - conditional release" .)