Workers possibly like collecting books (4)
I believe the answer is:
ants
'workers' is the definition.
(I've seen this before)
'like collecting books' is the wordplay.
'like' becomes 'as'.
'collecting' is an insertion indicator.
'books' becomes 'nt' (New Testament**).
'as' going around 'nt' is 'ANTS'.
'possibly' acts as a link.
(Other definitions for ants that I've seen before include "They live in a formicary" , "Six-foot insects" , "workers found returning" , "Industrious insects" , "Termites" .)