Understated or not immediately obvious (6)
I believe the answer is:
subtle
I believe this clue is a double definition.
'understated' is the first definition.
(I've seen this in another clue)
'not immediately obvious' is the second definition.
(I've seen this before)
(Other definitions for subtle that I've seen before include "Not immediately obvious, understated" , "Such distinctions are hard to see" , "Delicate and understated" , "Delicate, difficult to describe" , "Very fine, difficult to perceive or appreciate" .)