Drop the odd bit of slang (3)
I believe the answer is:
sag
'drop' is the definition.
(sagging is a kind of dropping)
'odd bit of slang' is the wordplay.
'odd bit of' means one should take alternating letters (I've seen 'odd bits of' mean this).
The alternating letters of 'slang' are 'SAG'.
'the' acts as a link.
(Other definitions for sag that I've seen before include "Sink, hang down" , "Subsidence" , "Sinking" , "Sink (under load)" , "Droop in the middle - it's gas" .)