Begin digging around river (5)
I believe the answer is:
intro
'begin digging around river' is the definition.
I can't tell whether this definition defines the answer.
'digging around river' is the wordplay.
'digging' becomes 'into' (I've seen this before).
'around' indicates putting letters inside.
'river' becomes 'r'.
'into' going around 'r' is 'INTRO'.
Can you help me to learn more?
(Other definitions for intro that I've seen before include "preface" , "Opening notes" , "Jazz piece" , "Song's opening" , "Opening bars to a piece of popular music" .)