Settle sources of rancour over offer, seeking talks (5)
I believe the answer is:
roost
'settle' is the definition.
(roosting is a kind of settling)
'sources of rancour over offer seeking talks' is the wordplay.
'sources of' indicates taking the first letters.
The initial letters of 'rancour over offer seeking talks' is 'ROOST'.
(Other definitions for roost that I've seen before include "residence" , "bed" , "(Bird) settle for night" , "(Bird) settle for sleep" , "Bird's night-time perch" .)