Fail to grasp just about everything in service manual? (6)
I believe the answer is:
missal
'service manual?' is the definition.
(I've seen this before)
'fail to grasp just about everything' is the wordplay.
I cannot really understand how this works, but
'fail' could be 'miss' (missing is a kind of failing) and 'miss' is located in the answer.
'about' could be 'a' (abbreviation in Chambers) and 'a' is present in the answer.
A single letter 'l' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'in' is the link.
Can you help me to learn more?
(Other definitions for missal that I've seen before include "A book of prayers used in mass" , "Church book covering all services in the year" , "Yearbook" , "Book used at Catholic mass" , "Religious book" .)