Cross what off right after? (6)
I believe the answer is:
thwart
'cross' is the definition.
(I've seen this before)
'what off right after?' is the wordplay.
'off' is an anagram indicator.
'right' becomes 'rt'.
'after?' means one lot of letters go next to another.
'what' with letters rearranged gives 'thwa'.
'thwa'+'rt'='THWART'
(Other definitions for thwart that I've seen before include "Hinder or prevent" , "Prevent from accomplishing something" , "Prevent from succeeding" , "Oppose successfully" , "Defeat" .)