Make ineffective northeastern wicket (6)
I believe the answer is:
negate
'make ineffective' is the definition.
(I've seen this in another clue)
'northeastern wicket' is the wordplay.
'northeastern' becomes 'ne' (abbreviation for northeastern).
'wicket' becomes 'gate'.
'ne'+'gate'='NEGATE'
(Other definitions for negate that I've seen before include "Cancel; invalidate" , "Show to be false" , "Opera by Puccini" , "Cause to have no effect" , "Nullify - deny the existence of" .)