Warn, unfortunately, in real time (5)
I believe the answer is:
alert
'warn' is the definition.
(alerting is a kind of warning)
'unfortunately in real time' is the wordplay.
I cannot really understand how this works, but
an anagram of 'real' is 'aler' which is within the answer.
'time' could be 't' (abbreviation) and 't' is present in the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for alert that I've seen before include "Thinking and acting quickly" , "Vigilantly attentive" , "Watchful and bright" , "'Attentive, vigilant (5)'" , "Wakeful, observant" .)