Adult follows mounted troops moving part of generator (8)
I believe the answer is:
armature
'moving part of generator' is the definition.
(rotating part of a generator)
'adult follows mounted troops' is the wordplay.
'adult' becomes 'mature' (similar in meaning).
'follows' is a charade indicator (letters next to each other).
'mounted' shows that the letters should be reversed in order.
'troops' becomes 'RA' (Royal Artillery).
'ra' reversed gives 'ar'.
'mature' after 'ar' is 'ARMATURE'.
(Other definitions for armature that I've seen before include "Rotating coil of an electric motor" , "Rotating coils of an electric motor" , "Rotating dynamo coil - a rum tear (anag)" , "Part of dynamo" , "keeper" .)