Absorb some of Rob's essay ... (6)
I believe the answer is:
obsess
'absorb' is the definition.
(thesaurus)
'some of rob's essay' is the wordplay.
'some of' indicates the answer is hidden within the clue.
'OBSESS' is hidden in the letters of 'robs essay'.
(Other definitions for obsess that I've seen before include "brood" , "Bosses (anag.)" , "Constantly worry (about something)" , "Plague" , "Control" .)