Reluctance to move, i.e. train broken down (7)
I believe the answer is:
inertia
'reluctance to move' is the definition.
(I've seen this before)
'i e train broken down' is the wordplay.
'broken down' indicates anagramming the letters.
'e'+'train'='etrain'
'etrain' anagrammed gives 'nertia'.
'i'+'nertia'='INERTIA'
(Other definitions for inertia that I've seen before include "'Sluggishness, indolence (7)'" , "Listlessness" , "lack of action" , "Apathetic state" , "Stagnating state" .)