Let go of key safety measure (4,6)
I believe the answer is:
fire escape
'safety measure' is the definition.
(route out of a building in a fire)
'let go of key' is the wordplay.
'let go of' becomes 'fire' (let go from a job).
'key' becomes 'escape' (key on a keyboard).
'fire'+'escape'='FIRE-ESCAPE'
(Other definitions for fire escape that I've seen before include "Emergency exit" , "rescue apparatus" , "Emergency way out" , "it could be a life-saver" , "steps outside" .)