Watchful; perceptive (9)
I believe the answer is:
observant
I believe this clue is a double definition.
'watchful' is the first definition.
(I've seen this before)
'perceptive' is the second definition.
(similar in meaning)
(Other definitions for observant that I've seen before include "adhering to religious practices" , "taking things in" , "with a keen eye" , "aware of surroundings" , "(Of music)using conventional keys" .)