Left convict during match preparing ground (7)
I believe the answer is:
tillage
'preparing ground' is the definition.
(tilling the land)
'left convict during match' is the wordplay.
'left' becomes 'l' (common abbreviation).
'convict' becomes 'lag' (I've seen this before).
'during' means one lot of letters goes inside another.
'match' becomes 'tie' (tie can mean a sporting fixture).
'l'+'lag'='llag'
'llag' placed inside 'tie' is 'TILLAGE'.
(Other definitions for tillage that I've seen before include "Cultivated land" , "Cultivation of the soil" , "Farmers undertake it" , "Farmers work at it" , "Preparing for cultivation" .)