Swore, staggered after head split? (5)
I believe the answer is:
vowed
'swore' is the definition.
(I've seen this in another clue)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for vowed that I've seen before include "Made a promise" , "Solemnly pledged" , "Solemnly promised" , "took the pledge" .)