Available set of books collected by pensioner (2,3)
I believe the answer is:
on tap
'available' is the definition.
(similar in meaning)
'set of books collected by pensioner' is the wordplay.
'set of books' becomes 'NT' (New Testament).
'collected by' means one lot of letters goes inside another.
'pensioner' becomes 'OAP' (old age pensioner).
'nt' inserted within 'oap' is 'ON TAP'.
(Other definitions for on tap that I've seen before include "Of liquid gas, ready to be drawn off" , "Available whenever needed" , "where C or H is seen?" , "Ready to be drawn off, like beer" , "Immediately available like beer in pub" .)