Lack of resistance in the end (6)
I believe the answer is:
dearth
'lack of' is the definition.
(I've seen this before)
'resistance in the end' is the wordplay.
'resistance' becomes 'r' (electronics abbreviation).
'in' means one lot of letters goes inside another.
'the end' becomes 'death' (the end of a life).
'r' placed into 'death' is 'DEARTH'.
(Other definitions for dearth that I've seen before include "Scarcity of thread" , "poverty" , "Scarcity, paucity" , "Severe shortage" , "want" .)