Cancel soft drink, after taking top off (5)
I believe the answer is:
quash
'cancel' is the definition.
(I know that quash is a more specific form of the action cancel)
'soft drink after taking top off' is the wordplay.
'soft drink' becomes 'squash' (I've seen this before).
'after taking top off' means to remove the first letter.
'squash' with its initial letter taken away is 'QUASH'.
(Other definitions for quash that I've seen before include "Overturn (judgment)" , "Put down" , "Subdue" , "Invalidate" , "Suppress or crush, say a rebellion" .)