An apt variety of long-grained rice (5)
I believe the answer is:
patna
'long-grained rice' is the definition.
I can't tell whether this definition defines the answer.
'an apt variety' is the wordplay.
'variety' is an anagram indicator.
'an'+'apt'='anapt'
'anapt' anagrammed gives 'PATNA'.
'of' is the link.
Can you help me to learn more?
(Other definitions for patna that I've seen before include "Rice town" , "Long-grain rice type" , "Long-grained rice type" , "Variety of long-grain rice" , "Source of long-grain rice" .)