Reserved books primarily examining small canines (7)
I believe the answer is:
coyotes
'canines' is the definition.
(coyote is a kind of canine)
'reserved books primarily examining small' is the wordplay.
'reserved' becomes 'coy' (I've seen this before).
'books' becomes 'ot' (Old Testament).
'primarily' says to take the initial letters.
The first letters of 'examining small' is 'es'.
'coy'+'ot'+'es'='COYOTES'
(Other definitions for coyotes that I've seen before include "North American predators" , "Prairie wolves" , "American prairie dogs" .)