Machine part replaced in barge (7)
I believe the answer is:
bearing
'machine part' is the definition.
(I know that bearing is a type of machine part)
'replaced in barge' is the wordplay.
'replaced' indicates anagramming the letters.
'in'+'barge'='inbarge'
'inbarge' is an anagram of 'BEARING'.
(Other definitions for bearing that I've seen before include "supplied by Air Traffic Control" , "Deportment" , "north?" , "Demeanour - direction" , "Carriage; suffering" .)