Hit book providing introduction to fretwork (4)
I believe the answer is:
biff
'hit' is the definition.
(I know that biff is a type of hit)
'book providing introduction to fretwork' is the wordplay.
'book' becomes 'b' (abbreviation for book).
'providing' becomes 'if' (eg 'providing it's sunny' means 'if it's sunny').
'introduction to' indicates taking the first letters.
The initial letter of 'fretwork' is 'f'.
'b'+'if'+'f'='BIFF'
(Other definitions for biff that I've seen before include "Punch" , "strike" , "Hard blow with fist" .)