Block second spinner (4)
I believe the answer is:
stop
'block' is the definition.
('stop' can be a synonym of 'block')
'second spinner' is the wordplay.
'second' becomes 's' (common abbreviation).
'spinner' becomes 'top' (something that spins).
's'+'top'='STOP'
(Other definitions for stop that I've seen before include "port of call" , "Wind up" , "Plug; cease" , "Cease; organ voice" , "Organ knob; get bus here" .)