Handy instruction book? (6)
I believe the answer is:
manual
This clue is a double definition.
'handy' is the first definition.
(I've seen this before)
'instruction book?' is the second definition.
(I've seen this in another clue)
(Other definitions for manual that I've seen before include "Relating to the hands" , "Done by hand, or a handbook" , "Operated by hand" , ""How-to" book" , "Guide" .)