Aware of later development (5)
I believe the answer is:
alert
'aware' is the definition.
(synonyms)
'later development' is the wordplay.
'development' is an anagram indicator.
'later' is an anagram of 'ALERT'.
'of' acts as a link.
(Other definitions for alert that I've seen before include "On the ball" , "Awake, attentive" , "In state of watchfulness" , "Wide awake and watchful" , "Watchful; warning" .)