Sailor’s English books missing (6)
I believe the answer is:
absent
'missing' is the definition.
(similar in meaning)
'sailor's english books' is the wordplay.
'sailor's' becomes 'ab's' (abbreviation for able seaman).
'english' becomes 'E' (abbreviation).
'books' becomes 'NT' (abbreviation for New Testament).
'abs'+'e'+'nt'='ABSENT'
(Other definitions for absent that I've seen before include "Not at a specified place" , "nowhere to be seen" , "AWOL" , "lack of attention" , "Missing, lacking" .)