Manual (8)
'manual' is the definition.
(instruction manual)
This is the entire clue.
(Other definitions for handbook that I've seen before include "Manual, reference" , "companion" , "Guide" .)
(Other definitions for textbook that I've seen before include "Reader for student" , "in a perfect way?" , "Student's manual" , "Manual for learners" , "Standard reference" .)
(Other definitions for user that I've seen before include "One operating something" , "Utiliser" , "Operator (of something)" , "Junkie's" , "Drug-taker" .)