Landed up in argument, producing knife (8)
I believe the answer is:
stiletto
'knife' is the definition.
(stiletto is a kind of knife)
'landed up in argument' is the wordplay.
'landed' becomes 'lit' (I've seen this in other clues).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'in' indicates putting letters inside.
'argument' becomes 'setto' (I've seen this before).
'lit' in reverse letter order is 'til'.
'til' inserted into 'setto' is 'STILETTO'.
'producing' acts as a link.
(Other definitions for stiletto that I've seen before include "Long thin knife" , "Kind of heel" , "Dagger; tapered heel" , "Narrow-bladed dagger" , "Type of shoe" .)