Warning of real disaster starting tomorrow? (5)
I believe the answer is:
alert
'warning' is the definition.
(I've seen this before)
'real disaster starting tomorrow?' is the wordplay.
'disaster' indicates an anagram.
'starting' suggests taking the first letters.
The first letter of 'tomorrow' is 't'.
'real' with letters rearranged gives 'aler'.
'aler'+'t'='ALERT'
'of' acts as a link.
(Other definitions for alert that I've seen before include "Vigilantly attentive" , "In state of watchfulness" , "Signal danger" , "Wakeful, observant" , "Wide awake and watchful" .)