Need to leave almost leaderless business (8)
I believe the answer is:
exigency
'need' is the definition.
(I have seen 'Urgent need ' mean 'exigency' so perhaps 'need' could also mean 'exigency')
'leave almost leaderless business' is the wordplay.
'leave almost' becomes 'exi' (I can't justify this - if you can you should give a lot more credence to this answer).
'leaderless' means to remove the first letter.
'business' becomes 'agency' (agency is a kind of business).
'agency' with its initial letter taken away is 'gency'.
'exi'+'gency'='EXIGENCY'
'to' is the link.
(Other definitions for exigency that I've seen before include "crisis" , "Urgent need" , "Demand" , "Sudden unforeseen need" .)