Loads rifles, taking time (6)
I believe the answer is:
stacks
'loads' is the definition.
(stacking is a kind of loading)
'rifles taking time' is the wordplay.
'rifles' becomes 'sacks' (I've seen this before).
'taking' means one lot of letters goes inside another.
'time' becomes 't' (abbreviation).
'sacks' enclosing 't' is 'STACKS'.
(Other definitions for stacks that I've seen before include "Orderly heaps as of hay" , "Ricks" , "Large tall chimneys" , "Tons" , "A lot (of hay?)" .)