Dog, really gutless, mine (8)
I believe the answer is:
colliery
'mine' is the definition.
(a colliery is a coal mine)
'dog really gutless' is the wordplay.
'dog' becomes 'collie' (collie is a kind of dog).
'gutless' suggests removing the centre.
'really' with its middle removed is 'ry'.
'collie'+'ry'='COLLIERY'
(Other definitions for colliery that I've seen before include "Where a coalminer goes to work" , "Mining complex" , "Coalmine and surrounding buildings" , "Coal-mining establishment" , "Pit" .)