Gaze at wild aster (5)
I believe the answer is:
stare
'gaze' is the definition.
('stare' can be a synonym of 'gaze')
'wild aster' is the wordplay.
'wild' is an anagram indicator.
'aster' is an anagram of 'STARE'.
'at' acts as a link.
(Other definitions for stare that I've seen before include "Look hard" , "Gawp" , "Long fixed look" , "bird" , "Look with fixed gaze" .)