Divert silicon carried up with potassium (9)
I believe the answer is:
sidetrack
'divert' is the definition.
(sidetracking is a kind of diverting)
'silicon carried up with potassium' is the wordplay.
'silicon' becomes 'si' (Si is the chemical symbol for silicon).
'carried' becomes 'carted' (carting is a kind of carrying).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'with' says to put letters next to each other.
'potassium' becomes 'k' (K is the chemical symbol for potassium).
'carted' in reverse letter order is 'detrac'.
'si'+'detrac'+'k'='SIDETRACK'
(Other definitions for sidetrack that I've seen before include "Provide diversion" , "Divert" , "lead away" , "Distract (from big issue)" , "Bit of railway" .)