Dismissing complaint after learner involved in smash (6,3)
I believe the answer is:
ruling out
'dismissing' is the definition.
(I've seen this before)
'complaint after learner involved in smash' is the wordplay.
'complaint' becomes 'gout' (gout is a kind of disease).
'after' means one lot of letters go next to another.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'involved in' is an insertion indicator.
'smash' becomes 'ruin' (both can mean to wreck).
'l' put within 'ruin' is 'rulin'.
'gout' after 'rulin' is 'RULING OUT'.
(Other definitions for ruling out that I've seen before include "Dismissing" , "Making impossible" .)