Stop insect holding article up (9)
I believe the answer is:
terminate
'stop' is the definition.
(terminate can mean to stop or bring to an end)
'insect holding article up' is the wordplay.
'insect' becomes 'termite' (termite is a kind of insect).
'holding' indicates putting letters inside.
'article' becomes 'an' (English indefinite article).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'an' in reverse letter order is 'na'.
'termite' enclosing 'na' is 'TERMINATE'.
(Other definitions for terminate that I've seen before include "Kill off" , "Put an end to, finish" , "Put an end to, discontinue" , "Stop" , "Cut short" .)