Discard stone — it upset child (8)
I believe the answer is:
jettison
'discard' is the definition.
(I know this)
'stone it upset child' is the wordplay.
'stone' becomes 'jet' (type of stone).
'upset' is a reversal indicator.
'child' becomes 'son' (male child).
'it' reversed gives 'ti'.
'jet'+'ti'+'son'='JETTISON'
(Other definitions for jettison that I've seen before include "Abandon, discard" , "Deliberately dump overboard" , "Throw overboard or discard unwanted material" , "Form of motor racing" , "'Throw away, cast overboard (8)'" .)