See about donkey’s rope (5)
I believe the answer is:
lasso
'rope' is the definition.
(I know that rope can be written as lasso)
'see about donkey's' is the wordplay.
'see' becomes 'lo' (archaic exclamation meaning 'look!').
'about' is an insertion indicator.
'donkey' becomes 'ass' (ass is a term for a donkey).
'lo' placed around 'ass' is 'LASSO'.
(Other definitions for lasso that I've seen before include "Cowboy's rope with sliding noose" , "What cowboy uses" , "Rope with 20" , "Cowcatcher" , "Rope for throwing" .)