Handy source of information (6)
I believe the answer is:
'handy' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for manual that I've seen before include "Working with the hands" , "Work-book" , "Relating to the hands" , "Operated by hand" , "reference book" .)