Guarantees end of strike with nurses working (7)
I believe the answer is:
ensures
'guarantees' is the definition.
('ensure' can be a synonym of 'guarantee')
'end of strike with nurses working' is the wordplay.
'end of' says to take the final letters.
'with' means one lot of letters go next to another.
'working' is an anagram indicator.
The final letter of 'strike' is 'e'.
'nurses' is an anagram of 'nsures'.
'e'+'nsures'='ENSURES'
(Other definitions for ensures that I've seen before include "guarantees" , "Makes safe or certain" , "Warrant" .)