Switches off or acts dismissed (5,3)
I believe the answer is:
turns out
'switches off' is the definition.
(synonymous eg when turning out a light)
'acts dismissed' is the wordplay.
'acts' becomes 'turns' ('turn' can be a synonym of 'act').
'dismissed' becomes 'out' (dismissed in cricket).
'turns'+'out'='TURNS OUT'
'or' acts as a link.
(Other definitions for turns out that I've seen before include "Empties" , "Gives order of the boot" , "as it happens" .)