Peace talks mostly failing to happen (4,5)
I believe the answer is:
take place
'happen' is the definition.
(I've seen this before)
'peace talks mostly failing' is the wordplay.
'mostly' means to remove the last letter.
'failing' indicates anagramming the letters.
'peace'+'talks'='peacetalks'
'peacetalks' with its final letter removed is 'peacetalk'.
'peacetalk' anagrammed gives 'TAKE PLACE'.
'to' acts as a link.
(Other definitions for take place that I've seen before include "Talk peace (anag) - happen" , "Occur, happen - assume position" .)