The turf thus initially dug (3)
I believe the answer is:
sod
'the turf' is the definition.
('sod' can be a synonym of 'turf')
'thus initially dug' is the wordplay.
'thus' becomes 'so' ('so' can be a synonym of 'thus').
'initially' indicates taking the first letters.
The first letter of 'dug' is 'd'.
'so'+'d'='SOD'
(Other definitions for sod that I've seen before include "Surface layer of ground with grass roots" , "Piece of peat or grass" , "A lulmp of turf" , "'Sward, turf (3)'" , "Lump of turf or unpleasant person" .)