Complete vexation at compromise (8)
I believe the answer is:
endanger
'compromise' is the definition.
(I know that compromise is a more specific form of endanger)
'complete vexation' is the wordplay.
'complete' becomes 'end' (complete means to finish or end).
'vexation' becomes 'anger' (I've seen this before).
'end'+'anger'='ENDANGER'
'at' is the link.
(Other definitions for endanger that I've seen before include "Threaten" , "Place into peril, jeopardise" , "Expose to injury or extinction" , "Jeopardize" , "To put one at risk" .)