Reportedly next in line’s bearing (3)
I believe the answer is:
air
'bearing' is the definition.
(both can mean an attitude or pose)
'reportedly next in line's' is the wordplay.
'reportedly' shows a homophone (sound like).
'next in line' becomes 'heir' (I've seen this before).
'heir' sounds like 'AIR'.
(Other definitions for air that I've seen before include "strain" , "Song - atmosphere" , "Vital thing" , "Light wind; song" , "Gas mix surrounding the earth" .)