Similar to gripping second book (4)
I believe the answer is:
amos
'book' is the definition.
(Old Testament book)
'similar to gripping second' is the wordplay.
'similar to' becomes 'as'.
'gripping' means one lot of letters goes inside another.
'second' becomes 'mo' (both are short periods of time).
'as' enclosing 'mo' is 'AMOS'.
(Other definitions for amos that I've seen before include "man" , "Prophet in the Bible" , "Biblical prophet and OT book" , "Old Testament book" , "American wild dog" .)