Hurry up in support for job security (6)
I believe the answer is:
tenure
'job security' is the definition.
'tenure' can be an answer for 'job' (thesaurus). I'm unsure of the 'security' bit.
'hurry up in support' is the wordplay.
'hurry' becomes 'run' (running is a kind of hurrying).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'in' means one lot of letters goes inside another.
'support' becomes 'tee' (I've seen this before).
'run' backwards is 'nur'.
'nur' inserted into 'tee' is 'TENURE'.
'for' is the link.
Can you help me to learn more?
(Other definitions for tenure that I've seen before include "(Right of) occupancy" , "Retune (anag.)" , "Length of time in office" , "Tenancy" , "Term for which to hold a position" .)