Pit (4)
'pit' is the definition.
(mining pit)
This is the entire clue.
(Other definitions for mine that I've seen before include "I made?" , "Coalpit" , "Pit; explosive device" , "Excavate for minerals" , "Explosive device concealed in ground" .)
(Other definitions for sump that I've seen before include "oil well?" , "Engine's oil reservoir" , "Into which liquids drain" , "Engine oil reservoir" , "It receives the engine oil" .)
'pit' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for colliery that I've seen before include "Coalmine and surrounding buildings" , "Pit" , "Grimethorpe?" , "Coal mine" , "Coal-mining establishment" .)