Finish second best (4)
I believe the answer is:
stop
'finish' is the definition.
(I know that finish can be written as stop)
'second best' is the wordplay.
'second' becomes 's' (common abbreviation).
'best' becomes 'top' (top can mean the very best).
's'+'top'='STOP'
(Other definitions for stop that I've seen before include "Blockage" , "Refrain from" , "Hold on" , "oboe, perhaps" , "Plug - organ knob - bus halt - period" .)