Reason for not calling and closing date (8)
I believe the answer is:
deadline
'closing date' is the definition.
(I've seen this before)
'reason for not calling' is the wordplay.
'reason for not' becomes 'dead' (I am not sure about this - if you are sure you should believe this answer much more).
'calling' becomes 'line' (I've seen this in another clue).
'dead'+'line'='DEADLINE'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for deadline that I've seen before include "Cut-off point" , "Fixed completion date" , "problem for the editor?" , "Latest time for completion" , "Target time" .)