Germanium depot's period of development (9)
I believe the answer is:
gestation
'period of development' is the definition.
(I've seen this before)
'germanium depot's' is the wordplay.
'germanium' becomes 'Ge' (Ge is the chemical symbol for germanium).
'depot' becomes 'station' (I've seen this before).
'ge'+'station'='GESTATION'
(Other definitions for gestation that I've seen before include "as before being transported by coach" , "Development over time" , "Period of development" , "Development of plan" , "Development (in womb)" .)