Heard in dispute: what calls for blessing? (7)
I believe the answer is:
atishoo
'what calls for blessing?' is the definition.
(people say 'bless you' after a sneeze)
'heard in dispute' is the wordplay.
'heard' indicates a 'sounds like' (homophone) clue.
'in dispute' becomes 'atissue' (synonyms).
'atissue' is a homophone of 'ATISHOO'.
(Other definitions for atishoo that I've seen before include "report of involuntary escape from trap?" , "Sound of a sneeze" , "hay-fever sufferer may interject this" , "Word to be sneezed at" , "25 sound" .)