Religious books penned by pensioner readily available (2,3)
I believe the answer is:
on tap
'readily available' is the definition.
(I've seen this in another clue)
'religious books penned by pensioner' is the wordplay.
'religious books' becomes 'NT' (New Testament).
'penned by' is an insertion indicator (inserted letters are penned in).
'pensioner' becomes 'OAP' (old age pensioner).
'nt' placed into 'oap' is 'ON TAP'.
(Other definitions for on tap that I've seen before include "Where you may see H or C" , "Freely available" , "Readily available" , "Ready to be drawn off, say beer" , "Available (for drinking?)" .)