Claim about working nurse (7)
I believe the answer is:
contend
'claim' is the definition.
(I know that contend is a more specific form of the action claim)
'about working nurse' is the wordplay.
'about' becomes 'c' (abbreviation for circa).
'working' becomes 'on' (on can mean working or activated).
'nurse' becomes 'tend' (tend can mean to nurse or look after).
'c'+'on'+'tend'='CONTEND'
(Other definitions for contend that I've seen before include "Compete; deal (with)" , "Engage in a struggle" , "Struggle; assert" , "fight" , "Tend NCO (anag.)" .)