Islander's baseline shot (8)
I believe the answer is:
balinese
'islander's' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'baseline shot' is the wordplay.
'shot' indicates an anagram.
'baseline' is an anagram of 'BALINESE'.
Can you help me to learn more?
(Other definitions for balinese that I've seen before include "Asian language" , "policy needs external support" , "Foreign language" , "Islanders" , "Indonesian" .)