Digging, so to speak (4)
I believe the answer is:
'digging so to speak' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for into that I've seen before include "Keen on, colloquially" , "Knowledgeable about" , "Curious about" , "Taking an active and lively interest (in something)" , "Showing enthusiasm for" .)