Generators died, rotating such a lot (7)
I believe the answer is:
dynamos
'generators' is the definition.
(dynamo is a kind of generator)
'died rotating such a lot' is the wordplay.
'died' becomes 'd'.
'rotating' says the letters should be written in reverse.
'such a lot' becomes 'somany'.
'somany' in reverse letter order is 'ynamos'.
'd'+'ynamos'='DYNAMOS'
(Other definitions for dynamos that I've seen before include "Electricity generators or energetic people" , "highly energetic people" , "Electricity producers" .)