Carry On Nurse is on late (6)
I believe the answer is:
extend
'carry on' is the definition.
(I've seen this before)
'nurse is on late' is the wordplay.
'nurse' becomes 'tend' (tend can mean to nurse or look after).
'is on' says to put letters next to each other.
'late' becomes 'ex' (prefix meaning former or onetime).
'tend' put after 'ex' is 'EXTEND'.
(Other definitions for extend that I've seen before include "Spin out" , "Straighten out" , "Spread - offer" , "Enlarge, widen" , "Hold out or stretch out" .)