Energy put into nurse's profession (6)
I believe the answer is:
career
'profession' is the definition.
(I've seen this before)
'energy put into nurse's' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'put into' is an insertion indicator.
'nurse' becomes 'carer' (I've seen this before).
'e' going inside 'carer' is 'CAREER'.
(Other definitions for career that I've seen before include "Not intellectual" , "race" , "job, but one that lasts for years?" , "Whole of employment" , "One's professional life" .)