Bundle of energy upset a lot of the same nurses (6)
I believe the answer is:
dynamo
'bundle of energy' is the definition.
(an energetic person)
'upset a lot of the same nurses' is the wordplay.
'upset' shows that the letters should be reversed in order.
'a lot of' becomes 'many' (I've seen this before).
'the same' becomes 'do' (abbreviation for ditto).
'nurses' is an insertion indicator (nurse can mean to hold onto or harbour).
'many' reversed gives 'ynam'.
'ynam' put within 'do' is 'DYNAMO'.
(Other definitions for dynamo that I've seen before include "Live wire" , "Tirelessly energetic type" , "It generates electricity" , "activist?" , "Device producing electrical power" .)