Plane is cutting weight in offload (8)
I believe the answer is:
jettison
'offload' is the definition.
(I know that offload can be written as jettison)
'plane is cutting weight' is the wordplay.
'plane' becomes 'jet' (jet plane).
'cutting' is an insertion indicator (some letters cut their way into a word).
'weight' becomes 'ton' (unit of weight).
'is' inserted inside 'ton' is 'tison'.
'jet'+'tison'='JETTISON'
'in' acts as a link.
(Other definitions for jettison that I've seen before include "Throw (into the sea)" , "Reject" , "Throw goods overboard, or discard what is unwanted" , "Eject" , "'Throw away, cast overboard (8)'" .)