Asian country lacking a prominent feature? (4)
I believe the answer is:
chin
'prominent feature?' is the definition.
(facial feature)
'asian country lacking a' is the wordplay.
'asian country' becomes 'China' (country in Asia).
'lacking' is a deletion indicator.
'china' with 'a' removed is 'CHIN'.
(Other definitions for chin that I've seen before include "'... up, stay cheerful (4)'" , "Prominent feature" , "Possible double feature?" , "Keep it up and be optimistic" , "Protruding feature" .)