Numerous staff getting on with uncertainty first (8)
I believe the answer is:
manifold
'numerous' is the definition.
(I've seen this before)
'staff getting on with uncertainty first' is the wordplay.
'staff' becomes 'man' (as in staffing or manning a particular place).
'getting on' becomes 'old' ('getting on a bit' means 'old').
'with' means one lot of letters go next to another.
'uncertainty first' becomes 'if' (I can't explain this - if you can you should give a lot more credence to this answer).
'old' after 'if' is 'ifold'.
'man'+'ifold'='MANIFOLD'
Can you help me to learn more?
(Other definitions for manifold that I've seen before include "Diverse like engine part?" , "of numerous parts" , "maths set" , "Abundant" , "Many and various" .)