Difficult to find (4)
(Other definitions for obscure that I've seen before include "Unknown or unclear" , "Cloudy or veiled" , "Indistinct or not well-known" , "Vague - mask" , "incomprehensible" .)
'difficult to find' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for elusive that I've seen before include "Vile sue is hard to catch" , "Difficult to catch or see" , "Difficult to find or catch" , "Use veil to be difficult to catch" , "Evasive or intangible" .)
(Other definitions for rare that I've seen before include "Very infrequent, lightly cooked" , "Very scarce, like undercooked steak" , "Meat that's lightly cooked" , "(Of meat) red" , "Not well done!" .)