Tough character reflected partially in Jacob Marley (5)
I believe the answer is:
rambo
'tough character' is the definition.
(I know that Rambo is tough)
'reflected partially in jacob marley' is the wordplay.
'reflected' is a reversal indicator (letters reflected back).
'partially' indicates the answer is hidden within the clue.
'obmar' can be found hidden inside 'in jacob marley'.
'obmar' in reverse letter order is 'RAMBO'.
(Other definitions for rambo that I've seen before include "Film series, starring Sylvester Stallone" , "Stupidly aggressive type" , "Film series hero" , "Senseless violent person" , "Sly feature" .)