Time-consuming story's less powerful (4)
I believe the answer is:
lite
'less powerful' is the definition.
'time-consuming story's' is the wordplay.
'time' becomes 't' (abbreviation).
'consuming' is an insertion indicator (consume can mean to bring in or absorb).
'story' becomes 'lie' (story can mean a fabrication).
't' put into 'lie' is 'LITE'.
(Other definitions for lite that I've seen before include "Low in calories" , "With fewer calories" , "Low in strength" .)