Skulking low life-force's no good (8)
I believe the answer is:
mooching
'skulking' is the definition.
(mooch and skulk can both mean to sneak around)
'low life-force's no good' is the wordplay.
'low' becomes 'moo' ('moo' can be a synonym of 'low').
'life-force' becomes 'chi' (I've seen this before).
'no' becomes 'n' (common abbreviation).
'good' becomes 'g' (abbreviation).
'moo'+'chi'+'n'+'g'='MOOCHING'
(Other definitions for mooching that I've seen before include "Hanging around, doing nothing in particular" , "Listlessly loitering" .)