Cancel patent on receptacle (8)
I believe the answer is:
overturn
'cancel' is the definition.
(overturning is a kind of cancelling)
'patent on receptacle' is the wordplay.
'patent' becomes 'overt' (both can mean obvious).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'receptacle' becomes 'urn' (I've seen this in another clue).
'overt'+'urn'='OVERTURN'
(Other definitions for overturn that I've seen before include "tip" , "Upset; abolish" , "Reverse previous findings" , "Empty out" , "Reverses, a decision say" .)