Machine in Liege needs to be altered (6,6)
I believe the answer is:
diesel engine
'machine' is the definition.
(diesel engine is a kind of machine)
'in liege needs to be altered' is the wordplay.
'to be altered' indicates an anagram.
'in'+'liege'+'needs'='inliegeneeds'
'inliegeneeds' with letters rearranged gives 'DIESEL ENGINE'.
(Other definitions for diesel engine that I've seen before include "lorry motor" , "Internal-combustion motor fired by compression" , "In which fuel is ignited by compression" .)