Books in scripture studies for mechanical routine (4)
I believe the answer is:
rote
'mechanical routine' is the definition.
(I've seen this before)
'books in scripture studies' is the wordplay.
'books' becomes 'ot' (Old Testament).
'in' means one lot of letters goes inside another.
'scripture studies' becomes 're' (Religious Education**).
'ot' going within 're' is 'ROTE'.
'for' is the link.
(Other definitions for rote that I've seen before include "By . . . . - from memory without thought" , "Habitual routine" , "Kind of memory - that tore it" , "Memorisation by repetition" , "By . . . . means by memory - that tore it" .)