Books kept by suspect townie investigated (4,4)
I believe the answer is:
went into
'investigated' is the definition.
(I've seen this before)
'books kept by suspect townie' is the wordplay.
'books' becomes 'nt' (New Testament).
'kept by' is an insertion indicator.
'suspect' indicates anagramming the letters.
'townie' is an anagram of 'wentio'.
'nt' placed into 'wentio' is 'WENT INTO'.
(Other definitions for went into that I've seen before include "investigated" , "Entered" , "Discussed" .)