Make a mistake with bearing messages (7)
I believe the answer is:
errands
'messages' is the definition.
(I've seen this before)
'make a mistake with bearing' is the wordplay.
'make a mistake' becomes 'err' ('err' can be a synonym of 'make a mistake').
'with' becomes 'and' (I've seen this before).
'bearing' becomes 's'.
'err'+'and'+'s'='ERRANDS'
(Other definitions for errands that I've seen before include "Working trips" , "shopping trips" , "Missions" , "Tasks involving journeys" , "Darners (anag.)" .)