Tips of oversized and really sharp blades (4)
I believe the answer is:
oars
'blades' is the definition.
(blade is the word of an oar in competitive rowing)
'tips of oversized and really sharp' is the wordplay.
'tips of' suggests taking the first letters (I've seen 'tip of' mean this).
The initial letters of 'oversized and really sharp' is 'OARS'.
(Other definitions for oars that I've seen before include "Soar around the rowers" , "Implements to propel a boat" , "Poles to propel a boat" , "Sweeps" , "Al --, US gangster" .)