Author lifting a piece of Spenser (3)
I believe the answer is:
'author' is the definition.
(to pen something is to author it)
'lifting a piece of spenser' is the wordplay.
'lifting a piece of' indicates a hidden word.
'PEN' is hidden in the letters of 'spenser'.
(Other definitions for pen that I've seen before include "International writers's organisation", "Put down", "Pound", "Animal enclosure", "Write".)