This is the 12117th most frequent Turkish word.
göstergesidir
"Indicator of" or "a sign of."
The word 'göstergesidir' is employed here to denote a characteristic or marker that signifies a particular attribute, in this case, persistence signifies success.
Başarı göstergesidir azim.
Persistence is an indicator of success.
Here, 'göstergesidir' is used to indicate that an observable phenomenon, the blooming of flowers, signifies the arrival of spring.
Baharın göstergesidir çiçeklerin açması.
The blooming of flowers is an indicator of spring.
In this sentence, 'göstergesidir' signifies that rising sales suggest or are evidence of an improving economy.