It’s found in rock — after support it gets to grow (5)
I believe the answer is:
agate
'it's found in rock' is the definition.
(agate is a type of stone)
I cannot understand how the remainder of the clue works.
(Other definitions for agate that I've seen before include "Banded ornamental stone" , "Type of quartz" , "Quartz variety" , "Onyx" , "Semi-precious quartz" .)