Went over only to be thwarted? (7)
I believe the answer is:
crossed
'thwarted?' is the definition.
('cross' can be a synonym of 'thwart')
'went over only to be' is the wordplay.
'went over only' becomes 'ed' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'be' becomes 'cross' (crossing is a kind of being).
'ed' after 'cross' is 'CROSSED'.
Can you help me to learn more?
(Other definitions for crossed that I've seen before include "Passed" , "Intersected; opposed" , "Traversed" , "Came over and < annoyed" , "Went over to the other side" .)