Army officer to slip and go to ground (8)
I believe the answer is:
collapse
'go to ground' is the definition.
(as in collapsing onto the ground)
'army officer to slip' is the wordplay.
'army officer' becomes 'col' (short for colonel).
'to slip' becomes 'lapse' (lapsing is a kind of slipping).
'col'+'lapse'='COLLAPSE'
'and' is the link.
(Other definitions for collapse that I've seen before include "Disintegration" , "Sudden breakdown" , "fold" , "Sudden fall" , "Break down - fall" .)