Stow initial leeks on ailing donkey (4)
I believe the answer is:
load
'stow' is the definition.
('load' can be a synonym of 'stow')
'initial leeks on ailing donkey' is the wordplay.
'initial' says to take the initial letters.
The first letters of 'leeks on ailing donkey' is 'LOAD'.
(Other definitions for load that I've seen before include "Burden, onus" , "that's put on commercial vehicle" , "Cargo - burden" , "Weight to be transported" , "Weight, source of pressure" .)