Cut off is suspended once leaders get delayed (7)
I believe the answer is:
isolate
'cut off' is the definition.
(both can mean to separate from others)
'is suspended once leaders get delayed' is the wordplay.
'leaders' indicates taking the first letters.
'get' means one lot of letters go next to another.
'delayed' becomes 'late' (I've seen this before).
The first letters of 'is suspended once' is 'iso'.
'iso'+'late'='ISOLATE'
(Other definitions for isolate that I've seen before include "Strand" , "Set apart from others" , "divorce" , "Also tie (anag.)" , "Ostracise" .)